Data Preparation. Warren Vick Europa Technologies Ltd.

Transcription

1 Data Preparation Warren Vick Europa Technologies Ltd.

2 What s your poison? We use a variety of methods and technologies Straw poll Hand drawn Non-GIS software (whole process) Esri PB / MapInfo Open source Other Your choice?

3 Ken Field, 2017

4 What is the best GIS for cartography? There is no single product or platform Where possible, use the right tool(s) for the job

5 Data Preparation Crossing the data chasm Not a task to be underestimated! Plan Document (especially if a repeated process) Source data Effort Results Disproportionate effort Data ready & ideal for use

6 What might need to be changed? Data Format Data Type (raster / vector) Data Projection Inherent styling Geometry joins / splits (Good example in my final presentation) Topology

7 Formats There are many formats for geospatial data: Based on published standards De facto vendor standards Data suppliers support limited number of formats Choose the best format for your software Some may be better than others: Active vs. transfer formats Know the limitations of your chosen format 2Gb file size limits are common

8 Projection Choosing the right projection for a map is very important Nearly all GIS software can reproject on the fly but this is a computational burden If you have a known destination projection, it is best to process to it Not all reprojection algorithms are the same which can lead to misalignment

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10 Spatial ETL Extract / Transform / Load Promoting greater interoperability Building a bridge over our data chasm Common tasks: Reprojection Transformations Restyling Other tasks: Geocoding Merging / conflict management Publishing / dissemination

11 Developing a workflow Programming/scripting vs. Visual workflows Programming/scripting is difficult but becoming more accessible. e.g. Python Visual programming is being made available on many technology platforms Building blocks (readers, transformers & writers) with an intuitive drag-and-drop user interface Examples

12 FME, Safe Software ( Alistair Aitchison

13 Geoprocessing in ArcGIS, Esri ( Just like programmers creating code, add comments to workflows so that they may be better understood by others.

14 Spatial Model Builder, ERDAS Imagine, Hexagon (

15 Graphical Modeller QGIS (

16 Introducing GDAL & OGR Open source software ( GDAL for raster processing OGR for vector data processing Multiple pronunciations Gee-Dhal vs. Goo-Dull, even Gee-Dull! Included with QGIS package ( Command line tools OSGeo4W Shell

17 Introducing GDAL & OGR Open source software ( GDAL for raster processing OGR for vector data processing Multiple pronunciations Gee-Dhal vs. Goo-Dull, even Gee-Dull! Included with QGIS package ( Command line tools OSGeo4W Shell

18 Hillshade Slope Base colour OS Terrain 50 Using gdaldem command

19 Using gdaldem command LIDAR Digital Surface Model (DSM)

20 GDAL/OGR Cheat Sheet GDAL Get vector information Print vector extent List vector drivers Convert between vector formats Print count of features with attributes matching a given pattern Read from a zip file Clip vectors by bounding box Clip one vector by another Reproject vector Add an index to a shapefile Add a spatial index Merge features in a vector file by attribute ("dissolve") Merge features ("dissolve") using a buffer to avoid slivers Merge vector files Get the difference between two vector files OGR Get raster information List raster drivers Force creation of world file Convert between raster formats Reproject raster Clip raster by bounding box Crop raster dimensions to vector bounding box Merge rasters Stack grayscale bands into a georeferenced RGB Export a raster for Google Earth Raster calculation (map algebra) Create a hillshade from a DEM Apply color ramp to a DEM Derek Watkins (

21 Thank you Warren Vick