EXPERIENCING THE MAKING OF AERIAL PHOTOGRAPHS USING A MODEL OF A SCHOOL

Transcription

1 EXPERIENCING THE MAKING OF AERIAL PHOTOGRAPHS USING A MODEL OF A SCHOOL Steve Pratchett (2004)

2 EXPERIENCING THE MAKING OF AERIAL PHOTOGRAPHS USING A MODEL OF A SCHOOL Steve Pratchett (2004) Introduction A number of uses can be made of such a model. It is simple enough to take a variety of colour photos showing the model from different angles, elevation, oblique and vertical. The pupils can be asked to identify the features and to work out where the photos were taken from. This enhances their awareness of the environment through the use of observational skills, presents them with a variety of ways of viewing an area, including the vertical (a useful introduction to looking at such photographs of their locality), and poses the problem of relating the smaller (reduced) photo to the original model, a basis for developing ideas of scale. (Catling 1985 p 55) The Key Stage 2 Geography N.C. states that children should be taught to use aerial photographs, e.g. (2d) Pupils should be taught to use secondary sources of information, including aerial photographs. The N.C. could be criticised for no reference to understanding these photographs. A parallel here would be teaching rote methods of subtraction in mathematics, without any understanding of such concepts as place value, decomposition, etc. Similarly, children can be taught to use aerial photographs but with little understanding of the viewpoint from which they were taken. Indeed, there is much for children to understand about aerial photographs that should go hand in hand with their use, e.g. What aerial perspective/viewpoint was the photograph taken from? (height? angle? direction?). What effect does height above the ground have on scale and area? What is the difference between a vertical aerial photograph and a map? (a photograph being only truly vertical over one point whereas a map is vertical over every point.) What happens if the angle at which an oblique aerial photograph is taken, is changed? What is the relationship between oblique and vertical perspectives and dead ground? Young children may have difficulty imagining viewpoints, and the complexities of the relationship between height and scale without the concrete Piagetian experience of creating their own aerial photographs where they physically experience the angles, distances and scales and how each affects the other. An added bonus is that this work on aerial photographs also generates an understanding of mapping concepts, as the following mini curriculum project illustrates. At first glance, practical aerial photography may only seem appropriate to Key Stage 2 but there is a fascinating example of this activity with nursery children described in a research project by Shevelan, Craddock, Spencer and Blades (2002) Learn to Look Down in Primary Geographer April 2002 Issue, p.p These three-and-a-half year olds take instant aerial photographs with a Polaroid camera of a cardboard model of Postman Pat s route through a village where he delivers letters. They demonstrated clearly that they were able to relate both oblique and vertical aerial photographs to objects and features at ground level. Experiencing the making of an aerial representation aided the children s understanding. They made fewer errors in task matching representation to model. ( Shevelan, Craddock, Spencer, & Blades 2002 p.31) The case study that follows illustrates that the experiences of making aerial photographs is just as relevant with 10-year-old children and resulted in accelerated understanding of scale, angle and aerial perspective. The activities also made a valuable contribution to children s numeracy, in particular, understanding of and skills in angles of inclination, angles of declination, rotation, parallelograms, distance and scale.

3 Key questions The following are some of the key questions addressed by the activities: What is a vertical and oblique aerial photograph and how are they made? How does our view of the school and its locality change with change of viewpoint? How does height above the ground affect the scale and area covered by an aerial photograph? How can a map be made from an aerial photograph and what are the similarities and differences between them? What is the relationship between the angle of declination and angle of elevation made between aeroplane in the air and child on the ground? How is our school orientated in relation to its immediate locality and which direction are the aerial photographs of our school taken from? Key concepts vertical, oblique, aerial photograph, change, viewpoint, angle, elevation, declination, scale, area, map, position, location, direction, bearing, dead ground, symbol Activity 1: Orientating the school model in relation to the actual school building and grounds A group of 8 eleven-year-old children at Pilgrim Primary School in Plymouth, Devon were shown the author's model of their school for the first time. Initially, this generated considerable excitement and discussion, focusing on features they recognised and omissions and similarities/differences between model and reality. There was much touching and they were disappointed the roof did not lift off to reveal the classrooms! The children orientating the model by sliding the base round until it was aligned correctly. The children then moved on to argue whether the model was correctly orientated in relation to the school. When they had agreed that it was not they turned the model around by sliding the cloth base across the floor. Using magnetic compasses the children then identified the 8 cardinal compass points and labelled these around the model.

4 Children using magnetic compasses to locate the cardinal points of the compass. Children labelling the 8 cardinal points of the compass around the school model.

5 To reinforce the compass bearings and the notion of "coming from the NW, SE..." etc., the children simulated 'fly-pasts' over the model using a large model aeroplane. As they did so they had to give a running commentary on what they could see below and in what order. Children simulating a 'fly-past' over the school model, approaching from a given compass bearing. Activity 2: Measuring angles of declination and elevation Using a model of an aeroplane and a 2D cut-out of a child linked by a length of elastic, the group of children investigated the angle of elevation (e.g. the degree of turn made by the child in looking up at the aeroplane). They then progressed to the angle of declination (e.g. the degree of turn made by the pilot or camera in looking down at the child). The aeroplane was fixed to a large 360 protractor board, fixed in turn to a larger board so that it was parallel to the floor where another 360 protractor board rested with a picture of a child in its centre. A piece of elastic connected the two, emanating from the centre of the two 360 protractors (the pilot's cockpit and the child's eye). When the 'child' was moved across the floor the elastic stretched and, when at fully extended, more could be released through the hole in the centre of the aeroplane's 360 protractor. Hence the 'child' and the 'aeroplane' could be stretched apart right across the hall or classroom. At various positions the angle of elevation and declination were read and always registered the same as each other. The difference between a vertical and oblique angle was thereby discussed in an experiential context.

6 Children and the author with the angle of declination/elevation model discussing the angle of turn made by the pilot looking down to take an aerial photograph. The children extending the elastic to lower the angle of elevation and declination.

7 The children completed this worksheet by using a 360 degree protractor to measure and record the angles of elevation/inclination and declination Activity 3: Taking vertical and oblique aerial photographs of a model A number of uses can be made of such a model. It is simple enough to take a variety of colour photos showing the model from different angles, elevation, oblique and vertical. The pupils can be asked to identify the features and to work out where the photos were taken from. This enhances their awareness of the environment through the use of observational skills, presents them with a variety of ways of viewing an area, including the vertical (a useful introduction to looking at such photographs of their locality), and poses the problem of relating the smaller (reduced) photo to the original model, a basis for developing ideas of scale. (Catling 1985 p 55) Having orientated the school model and identified the compass bearings around it, a group of eight children then prepared to take aerial photographs. They found that the optimum distance of 2 metres away ensured that the whole model was included in the frame. This necessitated the supervised use of a stepladder at the higher angles of elevation. Photographing smaller models or parts only would allow closer photography and standing height alone would suffice. Standing on chairs or tables should be avoided on health and safety grounds unless an adult holds the child while they take the photograph.

8 A group of eight children organising the taking of aerial photographs at 20 o intervals. The aerial photographs were taken at 20 o intervals as well as one at 90 o. To guide the child taking the photographs, others in the group used 180 o protractors and two long sticks joined at the end by a piece of string to set the angles. The task required the group to develop their organisational and collaborative skills in determining task allocation and turn-taking. Children taking turns in determining the angle of elevation for the aerial photograph. The photographs were developed by a 1-hour high-speed photographic service during lunch time while the memory of angles and viewpoint was still fresh in children's minds. They sequenced the photographs and began to analyse and compare them with the use of magnifying glasses. The main emphasis was upon evidence of change that occurred between the photographs taken from different angles and upon the difference between vertical and oblique views. In pairs the children began arranging and labelling a display of their sequence of aerial photographs around a 180 o arc.

9 A child using a magnifying glass to observe changes between aerial photographs taken from different angles. Children arranging their aerial photographs around a 180 o arc.

10 The photographs were then annotated with OHP pens and written accounts made of features observed, features hidden and changes that occurred around the arc. The concept of dead ground (areas hidden from view behind features in oblique photographs) was introduced to refine children's observations of and discrimination between vertical and oblique views. A close-up of children's observations made from aerial photographs of the model. The aerial photographs of the model were compared with those of the school taken from an aeroplane. As a result of their activities with the model the children were able to make informed deductions about: the direction the aeroplane had approached from; the angle of elevation/declination the aerial photograph had been taken from; the 'dead ground' in the photograph; whether the photograph was oblique or vertical. Clearly the children had progressed beyond simply using aerial photographs to understanding them; beyond merely identifying features on aerial photographs to a heightened awareness of the possible direction, angle and viewpoint from which they were taken. The conceptual understanding of oblique and vertical angles had been developed experientially through a relevant real life application and is a good example of integration between mathematics and geography. "Emphasis on arithmetical skills does not of itself lead to ability to make use of these skills in practical situations. It is only within a broadly based curriculum that the ability to apply mathematics is enabled to develop." (Cockroft Report 1982). Activity 4: Making maps from aerial photographs The Key Stage 2 Geography national Curriculum Programme of Study states: (2c) Pupils should be taught to use maps and plans at a range of scales (2e) Pupils should be taught to draw plans and maps at a range of scales

11 A4 colour photocopies were made from the vertical aerial photograph of the school model. The children overlaid these with transparent OHP sheets. Using OHP pens, they traced the shapes of features and used colours and patterns as symbols in the map that materialised. Two children using a transparent OHP sheet overlaid on an aerial photograph to produce a map. The children hinged the OHP sheet and the photocopy together with a piece of tape along the top so that they could lift the transparent overlay at any time without shifting its position. By slipping a piece of white paper in between the two so the progress of the map could be monitored. Children slipping a piece of white paper in between the transparent overlay and the vertical photograph to see the map forming.

12 Activity 5: Investigating map scale using models A group of children used an architect's model of their school and the surrounding streets built to a scale of 1:200. They were set the problem of how to take photographs from different heights above the model to see in what ways the vertical aerial photographs changed with altitude. The teacher held a toy figure hanging from a parachute over the architect's model to stimulate discussion about what the parachutist might see during the descent. The children soon realised the logistical problems of trying to raise a camera as high as the hall ceiling! Finally a child solved the problem by making the suggestion of standing the model on edge and then walking towards and away from it with the camera. A tape measure was produced so that a record could be kept of the vertical distance each photograph was taken above the model. The interval the children used was 50 cm. Three children using a camera and a tape measure to take vertical aerial photographs of an architect's model of their school. When the photographs were developed the children sequenced them in ascending order from the lowest altitude to the highest and began to discuss the changes that occurred between photographs. The children began to develop their understanding of map scale as they began to realise that: the photographs taken from a low altitude produced a large scale map with larger features but a smaller coverage of model area; the photographs taken from a high altitude produced a small scale map with smaller features but a larger coverage of model area. The children were not just using and comparing maps of different scales but understanding the relationship between scale and vertical distance from the ground.

13 Children, sequencing the vertical aerial photographs of the architect's model # in ascending order against a centimetre scale. The children selected three of the vertical photographs to make into maps. Using transparent OHP sheets as overlays taped along one edge, they traced over the photographs with OHP pens to produce plan views of the model. At intervals, the children could lift the transparent sheet hinged by the tape and slide a piece of white paper in between it and the photograph to monitor the progress of their map making. A child tracing a vertical aerial photograph of the architect's model onto a transparent overlay.

14 A child sliding a piece of white paper in between the transparent overlay and the photograph to check the progress of the map. When the three maps were completed they were compared for change of scale and coverage of land area. The most challenging task was then set; namely to work out the scale of the maps in relation to the model and the actual school itself. Using a centimetre ruler, the children measured the length of the school roof on the model and on the map. On the model the length was 8 cm and on one of the maps 1 cm. This gave a simple scale that the children easily understood e.g.: 1 cm on the map = 8 cm on the model (1:8). A further calculation was made to find the scale of the map in relation to real life. The model was built to a 1:200 scale. (1 cm on the model = 200 cm in real life). Hence, the 8 cm roof on the model = 1600 cm (16 metres). 1 cm on the map therefore = 1600 cm in real life (1:1600). This further extension of scale from map to model to real life was a demanding exercise for the children. Some of them need to use a trundle wheel and tape measures to calculate the length of the school roof before relating it to map and model. A child measuring the length of the school roof on the architect's model using a ruler. The finished piece of work used in a presentation and display in the hall, included children's calculations of map scale and the recorded observations of the changes occurring in the vertical photographs and maps with ascending and descending altitude.

15 A child measuring the length of the school roof on the map he has made from the vertical aerial photograph. The children's finished display of their vertical aerial photographs taken from different 'altitudes'.

16 Evidence for assessment was derived from teacher observation but also discussion and questioning with the children. The following are extracts of children's observations: "You get more in when you take a photo a long way away". "The school looks smaller in this one". "The school gets bigger and bigger, look here, when you come down (pointing to the vertical sequence of photographs)". "You only get the school and the football field in this one because you are close". "My school roof here (pointing to the map) is 1 cm on the model it is 8 cm bigger". In their written observations, which formed part of the display, two children wrote: "Ben's map is bigger than Mathew's map as Mathew's map fits more in because its on a smaller scale". Here is evidence that the children were beginning to formulate summary conclusions, which relate two variables e.g.: map scale and area. What they are struggling to express in words is that a small-scale map gives a greater coverage of ground area. They needed to go on and express the converse, e.g.: that a larger scale map gives a lesser coverage of ground area. The danger is that written evidence alone is taken as an indicator of geographical understanding. "In the context of Teacher Assessment, any learning task can be presented in a variety of ways - diagrammatic, written, oral, or through demonstration. A teacher can take full advantage of the range of possibilities to ensure that difficulties in communication are not confused with difficulties arising from the learning task itself." (Schools Examination and Assessment Council - SEAC. (1992) p.14 "Some children will achieve at a higher level if asked to present evidence in a certain way e.g. a child with poor co-ordination might perform better verbally than graphically. Focus on the attainment objectives of the task, the medium ideally should not mask what the child can do" Balderstone & Lambert (1992) p.18. The concrete and oral evidence generated by the activity suggested levels of conceptual understanding that were difficult to express without sophisticated use of written language. However the activity clearly provides a meaningful context in which to stimulate the development of more precise use of language to express observations findings and conclusions. Text & photographs Steve Pratchett (2004) References Balderstone, D., & Lambert, D. (1992) Assessment Matters. Sheffield: Geographical Association. Catling, S. (1985) Mapwork in Corney, G. & Rawling, E. (Ed.) Teaching Slow Learners Through Geography. Sheffield: Geographical Association SEAC. (1992) A Guide to Teacher Assessment: Pack C:A Source Book of Teacher Assessment. London: Heinemann. Shevelan, C., Craddock, S., Spencer, C. and Blades, M. (2002) Learn to Look Down in Primary Geographer April 2002 Issue,