Understanding and using your GPS Receiver (Version date: 2 February 2007)

Transcription

1 Understanding and using your GPS Receiver (Version date: 2 February 2007) Authors: Helen Durham and Katherine Arrell School of Geography, University of Leeds, UK Contents 1. Aims Learning Outcomes Introduction to nugget Setting up your GPS Preparing to navigate Basic functionality of GPS Track Log Waypoint navigation Find and Goto function Create and navigate a route Follow a bearing Change your co-ordinate system Get route statistics Advanced functionality Export location and track/route information Import map layers Using the electronic compass Getting altitude Conclusion Geocaching exercise Useful Web Links References...25 Understanding and using your GPS receiver. 1

2 1. Aims The aims of this resource are: To familiarise staff and students with the basic functionality of a handheld GPS receiver To introduce some of the more advanced features of a GPS receiver To guide users through simple activities and exercises to increase understanding of using GPS 2. Learning Outcomes Upon completion of this resource, you should: Know how to setup your GPS unit before use Be familiar with many of the basic features available on most GPS receivers Have an understanding of more advanced GPS functionality Have used your GPS receiver to hunt for a hidden cache (geocaching) in your local area 3. Introduction to nugget This nugget is one of a series of learning activities produced by the JISC/NSF-funded DIALOG-PLUS project to help staff and students understand the concepts of Global Positioning Systems (GPS). Other nuggets have been developed as part of this project on GPS Components, Sources of Error, Differential Correction and GPS Data Properties but this nugget will concentrate on the basic use of a GPS unit, including how to set it up before use, what it does, how to use it to find or store points of interest and how to import and export GPS data to and from a computer. The aim of this learning activity is to familiarise users with the basics of using a handheld GPS unit. As users of this nugget may all be using different makes and models of GPS units and the methods of entering commands (e.g. location of buttons and different menu structures) will differ, instructions within this nugget are very generic and you may need to refer to your GPS receiver manual to provide support and guidance. A Garmin etrexvista GPS receiver and the accompanying PC software, MapSource, were used Understanding and using your GPS receiver. 2

3 during the design and development of this nugget so some references in the learning material may be to this make, model and data management software. Additional advice on how GPS receivers works and step-by-step examples of the practical aspects of using a receiver can be found in the following text book, which is recommended as extra reading and has been extensively used in the development of this nugget: Letham, L. (2003) GPS Made Easy: Using Global Positioning Systems in the Outdoors. 4 th ed. The Mountaineers, Seattle, USA 4. Setting up your GPS Having decided that you are going to take your GPS receiver on your walking trip or you need it to collect and store significant points on your field trip or ground survey you first of all need to make sure that it is set up correctly and that it is fit for purpose. On the matter of fit for purpose you will generally just need to check that the unit is working properly and that you have spare batteries with you in case they run out during use, which could mean that you end up very lost (dangerous if you are in hazardous terrain or weather conditions) or simply that you are unable to complete your field work! Some GPS receivers just use AA batteries and some will take rechargeable batteries so check your instruction manual and make sure that you have spares and that the ones installed in the unit are new or are fully charged before setting out. Sometimes external power sources can be used, such as a power supply that plugs into the cigarette lighter in a car. With most GPS units any data collected and stored in your GPS memory is not lost if the battery fails. Prior to using your GPS receiver you need to know that it is set up correctly for use. A setup menu (possible accessed from the main menu page of your GPS) will allow you to select and set the following: Select appropriate map datum (e.g. WGS 84) Set coordinate system (e.g. UTM, latitude/longitude, OSGB) Set the data formats (e.g. metric, nautical, statute, degrees) Calibrate the electronic compass, if available on your GPS model Understanding and using your GPS receiver. 3

4 Download map data to your receiver (if available, within the limits of the GPS memory) More details about each of these individual features are available in the following sections of this nugget. 5. Preparing to navigate To find your location or to use your GPS receiver to navigate the first thing you have to do is turn on your receiver; use the instructions given in your user manual to find the power switch. If you wish to obtain your position then you will need to be outside in order for the receiver to track the satellites. Once turned on, your GPS receiver will automatically start to determine its location but requires a clear view of the sky and needs to receive signals from at least three satellites in order to fix its position and provide navigational guidance. Be aware that signals can be blocked by buildings, rocks, heavy tree cover or even people. If your GPS receiver is warning of a poor satellite reception, you will need to move more into a more open area. Once your receiver has a fix on at least three satellites your position will be displayed in the coordinate system as defined in the setup. However, there will always be some error in the location measured and the accuracy of the measurement is displayed on the screen. This information can be displayed in different ways but is commonly shown as + metres figure. This informs you that your location is within this buffer. You will usually have an error for your X and Y spatial coordinates and altitude estimate. Your position may be displayed as an accuracy circle where your location falls within the circle in this case, the smaller the circle the more accurate your location. Your receiver will have a number of display screen which you can cycle through and may include pages such as a satellite page, a map page, a navigation page, an altimeter page, a trip page and a main menu page, although these pages may be different depending on the make and model of your GPS unit. Familiarise yourself with the Understanding and using your GPS receiver. 4

5 display pages on your receiver, perhaps in consultation with your user manual, and make sure that you are comfortable with the location and action of each button or switch. Now you are ready to start using your GPS receiver. The next section of this nugget introduces the basic features and functionality of most GPS receivers. You do not necessarily need to work through the subsections in order but you may find this useful if you are new to the technology. 6. Basic functionality of GPS 6.1 Track Log This is a very simple function to implement which keeps a track of where you (and the receiver) have been - as you move around the GPS receiver automatically logs your position it s a bit like an electronic breadcrumb trail. This function can be used to allow you to reverse the track to retrace your steps to the beginning of your journey, or the track can simply be stored and used again to repeat your trip at a later date. The track log also stores information such as the time and distance between consecutive recorded points and may also store information on the elevation of the points recorded along the way. To use this function you need to ensure that the track log function is turned on before you set off, and as long as the receiver is continuously on throughout the journey it will record points automatically. The options on your receiver will allow users to set the record interval (how often a point is recorded) to be based on distance, time or an automatic mode (a combination of time and distance based on your speed and movement). The display window will show where you have been and, if you have a basemap downloaded to your GPS receiver, you will have greater awareness of your location and direction of travel. Figure 1 shows an example of a Track Log displayed on the Map display page of a Garmin GPS unit. Understanding and using your GPS receiver. 5

6 Figure 1: Example of a GPS display showing the path taken by the GPS unit user. Upon completion of your journey you may wish to retrace your steps to the beginning. To do this you can select the relevant option (e.g. Tracback) on the receiver and you will be navigated back to the start. On the other hand, if you wish to save your trip for future reference then you have the ability to save the recorded points into your GPS memory. Activity 1 Set up your GPS receiver, making sure the track log function is enabled. Navigate to the map display which shows where you are currently located. Walk a distance of at least 1km (your GPS receiver will have an odometer and will show you how far you have walked). Note the track that is recorded on the display as you walk. At the end of your walk select the function for retracing your steps and see if you can use your receiver to navigate your way back to the start point. 6.2 Waypoint navigation First of all we need to understand the term waypoint. Any point whose location you need to know and record is a waypoint, so for example if you wish to return to a location you have previously visited at a later time then that point can be stored as a waypoint in your GPS memory. Alternatively you may want to prepare a walking trip in advance and mark Understanding and using your GPS receiver. 6

7 route defining points along the way or your stopover points as waypoints. A waypoint is any location with known co-ordinates that has been allocated a name within your GPS receiver for future recognition and use. Waypoints can be added in a number of ways: Add your location at any point along your route or at a point of interest to your GPS memory Type in the coordinates (read off a map) and an appropriate name for each waypoint using the keypad on the GPS receiver Select a point from the basemap loaded on your GPS receiver Select a point from a map on your computer and then transfer the point to your GPS memory The number of waypoints that a receiver can store will vary depending on the make and model but careful planning prior to starting your trip will allow you to make sure that required waypoints are all stored on the receiver. When planning you trip you need to work out how many waypoints to add. Letham (2003) suggests storing waypoints for every 16km (10miles) when covering a journey on foot. However, you may feel that a particular trip requires a greater or lesser number experience will help you in this decision. Each waypoint that you add to your GPS memory needs a name allocating to it. If you wish you can just use the default name allocated to it by the receiver. It is preferable, however, to choose a name that reminds you of the location (e.g. Bridge if the waypoint is next to a bridge) but be aware that some GPS receivers limit the number of characters you use in the name. It may be possible to choose a symbol to be associated with the waypoint and you may be able to store a more detailed description of the point use these features if available on your receiver to help remind you of the location. Figure 2 is an example of some of the symbols available that you could mark your waypoint with [Note: this figure is taken from the waypoint property dialog box from the data management software, MapSource, which will be explained in greater detail later in this nugget. The symbols shown in this figure match the symbols available on the GPS receiver]: Understanding and using your GPS receiver. 7

8 Figure 2: Example waypoint symbols available in Garmin products Activity 2 Using your GPS receiver (and manual if required), add several waypoints to your GPS memory. All should be within a 2km radius of your current location. Waypoint 1: should be added by simply making your current location a waypoint. [Note: you will need to be outdoors and under an open sky to do this] Waypoint 2: The second point should be added by panning across your basemap loaded onto the receiver and selecting a local feature. Waypoint 3: This point should be measured from a map using a ruler to measure the coordinates as accurately as possible (again, make the point local to your current location) and type the coordinates into your GPS receiver. Waypoint 4 (optional): If your receiver can be linked to a PC with map data on, then you can add a waypoint to your PC map and download to your GPS memory. Make sure you give your points a suitable symbol and name. These points will be used in later activities. Understanding and using your GPS receiver. 8

9 6.3 Find and Goto function The Find and GoTo functions are very powerful tools and are fundamental to GPS navigation. Your GPS receiver will contain a menu button that allows you to find a waypoint, point of interest, city etc. stored in the memory. Some points you will have entered into the GPS memory yourself, such as waypoints, others may be features already installed on your GPS receiver such as cities. If your receiver will permit upload of maps from external sources (such as maps from the MapSource MetroGuide) then you may have access to points of interest such as Food & Drink, Lodgings, Attractions, Entertainment, Shopping, Services, Transportation, Emergency & Government and Manmade Places and you may be able to find individual addresses or intersections of two roads. You may have the option of selecting the point you wish to find by its name or by the nearest to your current location. See your instruction manual to work out how to use the Find facility and also the options your receiver offers in terms of selecting the feature you wish to find. Once you have selected a point, you may now use the receiver to navigate you there. This is called GoTo and either the map page or the navigation page can be used to guide you to your chosen point. The navigation page will display the name of your destination and how far away it is. A Bearing Pointer will also show you the direction you need to travel in. Once you are on the move, an indication of how long your journey will take is displayed and you may also choose to display the speed you are travelling or your heading or other types of data you have selected. If you wish you can use the Map page of your receiver which shows your movements and a direct route will be displayed as a line on your map from the current location to the destination. Your receiver will also indicate when you are close to your destination with a message. Understanding and using your GPS receiver. 9

10 Activity 3 You have previously stored a number of waypoints in your GPS memory. Use the Find function on your receiver to find one that is within walking distance of your current location. Assuming that you are still in the vicinity of that point, use the GoTo Function to navigate your way to the point. 6.4 Create and navigate a route A route is a series of waypoints that define a particular journey. Like the Find and GoTo functions the Route function guides you to the next waypoint but it is slightly more powerful in that once you arrive at the first waypoint it automatically gives you directions to the next waypoint in the Route series, and so on until your reach your final destination. Before starting a journey you need to make sure all significant points along your route are stored as waypoints in the GPS memory. Then select the Route function from the menu and create a new route this will require you to select the waypoints in the order that you wish to visit them on your journey and the receiver will take you to the Find function to enable selection of the waypoints or points of interest. An easier way of creating a route is by using a map program on your PC (such as MapSource), if you have access to such software and if your GPS unit allows data to be downloaded to it. The advantage of this approach is that it allows you to select your points off a detailed map, using a larger screen and probably higher resolution, with peripherals such as keyboard or mouse to aid in the selection and add process. It will also allow you to create more complex routes. Once a route has been built on the PC it can simply be downloaded to your receiver and off you go! Figure 3 is an example of a route as defined in MapSource. The waypoints were marked on the computer map and a route was defined. In the first figure below, it is assumed that the journey is to be in a car so the route follows the roads: Understanding and using your GPS receiver. 10

11 Figure 3: Route (via road) defined in Garmin s MapSource MetroGuide Alternatively, you may be walking the route and wish to know the quickest and most direct route in which case you can set the Route function to show you the waypoints linked by straight lines (Figure 4): Figure 4: Direct route defined in Garmin s MapSource MetroGuide You can then view the details of the route as descriptive text which can be printed out and used to guide you on your journey. The directions when travelling by road would look something like that shown in Figure 5: Understanding and using your GPS receiver. 11

12 Figure 5: Descriptive text for route by car Or the directions when walking and wishing to take the most direct route would be similar to Figure 6: Figure 6: Descriptive text for direct route Once you have defined your route you then need to be able to navigate along it. Like the GoTo function you can use the map page or the navigation page to guide you. The map page will show you where you have been, the route line you need to be following and the position of the waypoints along the route. If you prefer to work from the navigation page then you can use the compass and the Bearing Pointer to give you guidance. You do not Understanding and using your GPS receiver. 12

13 need to commit yourself to any one display; you can easily switch between the two displays as you move along your route. Activity 4 Explore the Route function on your GPS receiver can you find out either from the GPS or the manual what are the maximum number of waypoints you can use in a route? 6.5 Follow a bearing You may wish to follow a bearing when using the GoTo or Route functions on your GPS receiver. A bearing is simply the compass direction between your current location and your next waypoint or destination. Bearings are relative to the north pole (true north) or magnetic north (so you need to know what the North setting on your receiver is before setting off on a journey) and are therefore given in degrees between 0 and 360. The navigation page of your GPS receiver provides guidance when trying to reach a destination stored in the GPS memory. Information such as the name of the destination point (which may be a waypoint), the straight line distance to that point, and estimation of the travel time, a compass ring, a Bearing Pointer and some data fields which are usually selectable to suit your journey and requirements. The page consists of a compass ring which rotates as you turn so that you can always work out your direction of travel. This compass ring may or may not work as a magnetic compass when you are stationary; only GPS receivers with a built-in electronic compass will continue to work as a magnetic compass if you are not moving. If your GPS has an electronic compass then you need to calibrate it (outdoors) prior to the very first time of using and subsequently whenever you change the batteries in the receiver. Another point to remember is that it is advisable to hold your GPS receiver as level as possible whilst taking compass readings and items which generate magnetic fields can also affect the reading so should be avoided. The arrow on the compass ring is called the Bearing Pointer. During navigation this arrow always points to your destination, wherever you may be at that time. If the arrow is pointing forwards (there may possibly be a fixed line on the compass ring which the Bearing Pointer needs to be aligned with) then you know you are travelling in the correct direction. If you go off-course then the arrow will rotate away from straight ahead. So if, Understanding and using your GPS receiver. 13

14 for example, the arrow has moved round to the left then turn to the left until the arrow is pointing ahead again. Following this procedure will eventually guide you to your destination. What do you do, however, if there is an obstacle on your journey which you cannot pass? For example, maybe you find that there is a river on your route and it is too wide and too deep for you to cross. In those circumstances you need to find a passable route (such as a bridge) and then once on the other side of the obstacle you can use the Bearing Pointer to continue the guidance. Other information included on the navigation page that may help you follow your bearing are the distance to the destination and an estimation of the time it will take for you to complete that leg of the journey, based on your current or average speed of travel. Other data that may be displayed on that page include heading, odometer, times of sunrise or sunset, time of the day, vertical speed, maximum speed and so on. The selection will depend on your receiver make and model and instruction on how to select the data fields you wish to display will vary so you should consult your manual for details. 6.6 Change your co-ordinate system Choosing and setting the correct or most appropriate coordinate system on your GPS receiver is very important. A spatial coordinate is a description of a position, using numbers and/or letters and when you use a receiver you will see that when it is receiving a satellite signal it displays your current location as spatial coordinates. To use this information to prevent you becoming lost, however, it is important that you know what coordinate system those coordinates are being reported in. The coordinate system describes the coordinate grid and the way that the coordinates are written. This determines how they will fill geographical space. Some of the more common coordinate grids you may use are latitude/longitude, Universal Transverse Mercator (UTM) or if you are in Great Britain (GB) you are most likely to use the British National Grid. Many countries have their own coordinate grid and if you examine the coordinate system setup on your GPS you will see a selection you can chose from, to suit your location. The other setting you need to make sure is correct on your GPS receiver is the map datum this is a standard reference point that every point on a map is a known distance and height from. In North America the two most common datums are North America Datum 1927 (NAD 27) and World Geodetic System 1984 (WGS 84). GB has its own Understanding and using your GPS receiver. 14

15 datum that is used with the National Grid and that is the Ordnance Survey Datum (OSGB36). If you are elsewhere in the world you need to check that the datum set on your GPS receiver corresponds with your other spatial data e.g. maps loaded. A map can have several coordinate grids marked on it but it will only ever have one datum and if you wish to consult your map and cross reference it with your GPS readings then it is important that they match. You can find out more about coordinate grids and datums used in GB from the OS guide to coordinate systems in Great Britain at (note: a PDF version of the guide is available from that URL) registration is not necessary to view this guide. Before you start a trip you will probably examine a map of the local area. In order for you to be able to cross reference your position as reported by your GPS receiver with your position on a map you need to make sure the two are using the same coordinate system. If you are in the GB then it is most likely that you are looking at an Ordnance Survey (OS) map which uses the British National Grid. The whole of GB is split into 100km square sections which have been assigned a two letter code. Each 100km square is then divided into 1km squares and a location is described by an easting and northing in metres with respect to a false origin (400km west and 100km north of the true origin at 49 N 2 W, just south-west of the Scilly Isles). For further information, the OS provide an online guide (registration is not necessary) to the National Grid reference system at If you go to the setup menu on your GPS receiver and go to the Units page you will find you can select British Grid as your coordinate grid (it may be called position format or something similar rather than coordinate grid) and your datum as OSGB36. Take this opportunity to set your receiver to these settings now if it not already done so. Refer to the manual for specific instructions on how to select and change settings. Activity 5 You can change coordinate systems and map datums mid-journey if that is necessary (for example, if you are also referring to a series of maps which have different grids or Understanding and using your GPS receiver. 15

16 datums). We will now undertake a very simple exercise to make sure you are familiar with the coordinate systems and how to set them on you GPS receiver. Make sure your GPS is set to the OS National Grid and that the datum is also the OS GB datum. Input these waypoints (including their names) at the following coordinates. [Hint: you will need to go into mark waypoint, move the cursor to the location field and then manually input these coordinates using the keypad on your GPS]. If your GPS unit will not allow as many characters as given in the Name column below then abbreviate the name further. Grid: British National Grid Datum: Ordnance Survey Great Britain Name Symbol Description JohnOGroat Waypoint John O' Groats LandsEnd Lodgings Lands End Hotel LeedsUni University University of Leeds ManT1 Airport Manchester Terminal 1 Snowdon Summit Snowdon Summit, Wales Position (OS British National Grid) ND SW SE SJ SH Position (longitude/latitude) Once these five waypoints have been saved then go back into the settings menu and change the coordinate grid to longitude and latitude (hddd mm'ss.s" hours, degrees, minutes and seconds) and the datum to WGS 84. Understanding and using your GPS receiver. 16

17 Now use the Find function to find each of the waypoints in turn. The location field in the waypoint display will now show the location in longitude and latitude. Against each waypoint record the new coordinates. 6.7 Get route statistics Your GPS receiver will probably include a page which will allow you to monitor how far you have moved, how long it has taken, your average moving speed, along with other statistics that you choose to be displayed according to your preferences. Figure 7 is an example of the statistics page (or trip computer page as it is called on Garmin units): Figure 7: Example of the Statistics page on a GPS unit Prior to starting a new trip you should clear old data from the statistics page and reset the data fields so that everything starts as zero; you will find the reset option on the page option menu. Make sure that you only reset the old statistics there may be the option to clear saved tracks, waypoints and routes from the same option page and you do not necessarily want to delete these! Activity 6 Find the statistics or trip computer page on your GPS receiver and explore the data fields that you can select to be displayed and investigate how to reset the statistics before a new trip. If you decide to reset these data fields at this point make sure you do not delete any tracks, waypoints or routes, particularly if this receiver is not your own property and is used by other members of your organisation or institution. Understanding and using your GPS receiver. 17

18 7. Advanced functionality This section of the learning activity will concentrate on more advanced functions which are only available on some makes and models of GPS receivers. An introduction to these functions, even if the receiver you are using does not include them, will help in your understanding of GPS. 7.1 Export location and track/route information It is possible to link your GPS receiver to a PC to allow maps and data to be transferred between the two. The next subsection will provide further information on uploading more detailed maps from your PC to your GPS unit but this section will concentrate on downloading data collected in the field, in the form of waypoints and tracks to your PC. The instructions are very brief because users will have different GPS units and software so reference to the user manuals and software instructions will be required to obtain specific instructions. To export the data from your GPS receiver to PC you will need a PC interface cable which may have been supplied with the receiver or may be purchased separately. You will also need a PC with a data management software (such as MapSource) installed. For more information on MapSource products go to If you are not using a Garmin unit then you will need to contact your GPS supplier to find out the equivalent product to support exporting GPS data. MapSource (or equivalent) will need to be installed on your PC before trying to download data from the GPS unit to it. You will then need to link the receiver to the PC with the PC interface cable, as described in the instructions supplied with MapSource. Once the two pieces of equipment are linked, and your receiver is turned on, it is possible to select waypoints, tracks and routes, collected and stored in your GPS memory, and download them to your PC your software instructions will guide you through this process. Understanding and using your GPS receiver. 18

19 An example of what a track log, collected on a GPS receiver will look like once transferred to MapSource on a PC is given here. Figure 8 is an extract of a track log as it appears when downloaded to GPS data management software (in this case MapSource). The panel on the left shows information on each saved track and the map on the right displays the location on a basemap of the points within that track. Figure 8: Example of Track Log downloaded to a PC Each saved track can be explored further by selecting a log and viewing the track properties as shown in Figure 9. It can be seen that information on the altitude, leg length, leg time, leg speed, leg course and position, along with track statistics, can all be extracted. Understanding and using your GPS receiver. 19

20 Figure 9: Example of Track Properties The vertical track profile can also be displayed, i.e. the altitude over track distance (Figure 10): Figure 10: Example of Vertical Track Profile Understanding and using your GPS receiver. 20

21 7.2 Import map layers Another useful function is the ability to download map data from products such as MapSource Metroguide to your GPS receiver. This will replace any basic map data supplied on the GPS but will be much more detailed, including minor streets, and will allow users to find street addresses or points of interest. Sometimes the map data is downloaded onto your GPS internal memory or some receivers have removable memory cards to provide a more flexible way of managing your downloadable maps. The more basic GPS receivers will not allow downloading of map data to its memory at all and users of such receivers will need to rely on the basic map information pre-loaded into its memory. 7.3 Using the electronic compass A GPS receiver without a built in electronic compass cannot be used as a compass unless you are moving as soon as you are stationary it can no longer calculate the direction you were heading in and this can be tested by standing still and then slowly turning around on the spot. If you try this the bearing on the compass will not change. However, some GPS receivers have an electronic compass which will show you your bearings whether you are moving or standing still. This is because the receiver is using the earth s magnetic field to measure your bearing relative to the North Pole. So, like a magnetic compass, if you stand in one spot and turn around slowly, the compass ring will indicate the direction of north. For accurate readings the receiver should be held level to the ground. Your GPS receiver may well have a bubble level built in to ensure it is held level, or a warning may be displayed if the receiver is tilted or if the compass has not been calibrated. Using your electronic compass close to a magnetic field will affect its accuracy and should be avoided! 7.4 Getting altitude You can use your GPS receiver to obtain information on your altitude but, as with the electronic compass, a built in altimeter gives a much more accurate measurement. An altimeter is a device for measuring distances above sea-level. It works by measuring Understanding and using your GPS receiver. 21

22 changes in the barometric (or atmospheric) pressure there is a higher pressure at sea level than at the top of a high mountain so as you climb or descend on your journey the altimeter calculates you altitude based on these changes. Atmospheric pressure is measured in inches of mercury, millibars or kilo-pascal and you can choose your preferred units from the setup menu on your receiver. For greatest accuracy you may need to calibrate your altimeter by inputting your known altitude at the beginning of your journey but if this is not possible, or you do not know your height position, the receiver may be able to automatically calculate it based on the satellite signals. It must be noted that the accuracy of the altimeter reading, however well calibrated, can be affected by the weather changes in the weather alters the atmospheric pressure which in turn alters your reading. If you have a built in altimeter then it is probable that you have a page which displays a variety of elevation information, such as current elevation, rate of ascent/descent, altitude profile over distance or time or a profile of pressure changes over time. You will usually be able to set up this page in your preferred format from the page options menu. 8. Conclusion Out of necessity this training nugget has been generic in nature but if used alongside your GPS user manual should have given you some insight and experience into using your handheld GPS unit. Hopefully, after working through this learning material you are in the position of using your GPS unit in a variety of applications, and have gained confidence and ability for day-to-day usage which will increase with practice. The following exercise will consolidate some of the training from this nugget and will require you to use a number of the basic functions and features on your receiver. This exercise is going to introduce you to the international game of Geocaching and you will be required to use your GPS receiver to find some treasure. 9. Geocaching exercise This exercise can be carried out at an individual level or could be a group-based activity. Understanding and using your GPS receiver. 22

23 First of all, what is geocaching? The geocaching website defines it as follows: Geocaching is an entertaining adventure game for GPS users. Participating in a cache hunt is a good way to take advantage of the wonderful features and capability of a GPS unit. The basic idea is to have individuals and organizations set up caches all over the world and share the locations of these caches on the internet. GPS users can then use the location coordinates to find the caches. Once found, a cache may provide the visitor with a wide variety of rewards. All the visitor is asked to do is if they get something they should try to leave something for the cache. ( accessed 19/07/05) This exercise gives you the opportunity to go and hunt for a local cache. Participation in the internet version is not required but the geocaching website will be used to provide information on the location of caches in your area and give you more information on the game itself. Go to (for the UK and Ireland) or (USA). If you live outside of these countries, investigate whether a geocaching website exists for your country. First of all, explore the website so that you understand the basics of geocaching and ensure that you read any rules applicable to your country. Then follow the links to seeking a geocache (you will end up on the US website at You have a box into which you can put your postcode/zip code or use one of the other search facilities to bring up a list of caches in your area. You do not have to register to look at the available caches but if you wish to participate in the international game and potentially hide caches yourself or upload information on caches you have found then you will need to follow the simple registration process. The exercise you are required to undertake is to find a geocache. You do not need to participate in the geocaching website game (i.e. you do not need to take something from the cache and leave something in its place if your do not wish to). Certainly don t take something from the cache and NOT leave something in return - that is not part of the geocaching etiquette! Nor do you need to add anything to the log book on the website if Understanding and using your GPS receiver. 23

24 you prefer not to. However, as part of your assessment you will be required to submit a report to your instructor on finding your geocache. First of all you need to select a geocache that is within travelling distance depending on your location and access to transportation. The webpage for the cache will include longitude and latitude and also coordinates from an appropriate coordinate system (e.g. if you are UK based then the cache details will also include British Grid coordinates.) You need to add those coordinates as a waypoint in your GPS receiver and then simply use your receiver to find your chosen geocache. Your submission needs to include a summary of the geocaching exercise, a print-out of the geocache information of your chosen cache from the geocache website, some evidence of having found the geocache (such as a photo) and a short report on how easy you found the geocache and evaluate how useful the receiver was in actually finding the cache - do you think you could have found your chosen cache just by using a map and the hint on the website? 10. Useful Web Links The National Grid map reference system; an OS online guide - Garmin GPS MapSource - A guide to coordinate systems in Great Britain - Geocaching website (UK and Ireland) - Geocaching website (USA) - Understanding and using your GPS receiver. 24

25 11. References Geocaching, Frequently asked questions. accessed 19/07/05 Letham, L. (2003) GPS Made Easy: Using Global Positioning Systems in the Outdoors. 4 th ed. The Mountaineers, Seattle, USA Understanding and using your GPS receiver. 25