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[flyte] - [GIS Fundamentals Vol.1]

GIS Fundamentals

Geographical Information Systems (GIS) are central to the enormous growth of the drone industry, allowing it to permeate into the high-growth verticals seen today. As the drone industry does now, GIS has a long track-record of transcending industries, creating standards and enabling processes for large-scale management and analysis of location-based data.

As a commercial drone pilot, it is important to develop GIS knowledge and skills because nearly all governments bodies (local councils, environmental agencies, urban planning) as well as an enormous range of businesses have at least some degree of GIS capability subsequently requiring geospatial data.

For geospatial datasets to be useful to them, they must be provided to the correct expectations and requirements of the organisation. Most commonly this is ensuring the correct GIS file formats, suitable map projections and scale.

  

1. Rasters and Vectors

Geospatial data can be divided into either Vector or Raster datasets. Raster datasets are anything laid out in a continuous gridded form. Aerial imagery is a prime example of this. With a simple RGB camera, each pixel can be represented by a square on the grid. Digital Terrain/Elevation Models are most commonly managed using this structure. These are typically stored in formats such as GeoTiff and ESRI’s own ASCII file format.

Vector datasets are distinct from grids. Their extents are limited to the extent of a specific object/entity they represent and are not continuous. They are commonly used to delineate powerlines and map areas of specification vegetation.

A vector is not exclusively a single line, but can also be singular points, or a polygon shape positioned on a map. They are used for analysis of topology and connectivity as well as to define contour lines on topographical surveys. The standard file format representing vector data is known as a ShapeFile.

 

2. The ShapeFile

Screen Shot 2017-06-30 at 17.27.58.pngFigure 1. Three types of shapefile. Points, Polylines and Polygons. 

This is the GIS standard for representing geospatial vector data.

Developed and maintained by ESRI, it has been universally adopted by government institutions and businesses worldwide. It is often the form your logged flight paths and associated telemetry are recorded.

The simplest form of geospatial vector data is the Point. This is simply an X Y coordinate location po- sitioned on a map. Data is then attached as associated attributes represented at the point’s singular X Y location. A MultiPoint shapefile is one singular shapefilewhich include more than one point; these do not have to be connected, just included within the same shape le.

Polylines are ordered sequences of connected points (i.e. with lines between the points in a specfied order.  Again, within one singular Shapefile there can be multiple sets of a separate polylines.  Imagine the telemetry of your drone’s ight being represented this way, with battery level attributes throughout the fight also included within the same file.

 

Polygons are areas comprised of at least three points in a closed loop. The order of vertices is crucial and determines the shape and size of area being represented on the map.

It is important to note that the ShapeFile itself is comprised of four standard files (but depending on application, others will be required:

Screen Shot 2017-06-30 at 17.43.31.pngFigure 2. the key components of  a ShapeFile

 

Note: most importantly, if moving/sending ShapeFiles, send all files associated with the ShapeFile. They support the attributes within the .shp file. To learn more, the original whitepaper by ESRI can be accessed here.

3. Projections

Projections are an essential consideration because they determine how the three-dimensional real world data and imagery are projected and rescaled accurately as a “flat” digital map.

When creating data, it is essential to ensure that you’ve created it under the right projection, matching with that of the base map and data.

With each project, always check that projections remain consistent and correctly match they datasets you are working with. For example, if creating a new shapefile, ensure the project is consistent with the rest of the project.

4. Geo-Referencing and importance of Ground Control Points

Geo-Referencing is adding spatial context to a normal image (i.e. an aerial image stored as a JPEG).  By georeferencing it, you are turning a regular aerial image into a spatially acc raster file. Key to this is selecting good ground control points.  

These are features identifiable on both on aerial image and the map, from which the rest of the image is stretched and skewed over the spatially accurate. If you do not have your GCP during the flight, georeferencing using identifiable features post-flight can offer solutions to positioning errors and skewed imagery.  

without0bg-03.pngFigure 3. Basic RTK setup between drone, GNSS and active ground control point (GCP). 

5.Where can you apply this GIS knowledge? 

Fortunately, there is excellent open-source GIS software built and maintained by the GIS community. The most commonly adopted and accessible platform is called QGIS. There is also ESRI's ArcGIS, who have a series of drone technology integrations available to pilots namely Drone2Map

Both platforms enable drone pilots to create and manipulate their data, creating vector files from their imagery, correcting images if there were satellite errors and generally enabling them to manage larger geospatial datasets.

This platform is ideal for manually delineating objects within aerial images, tracing power lines or roads for example and representing them as shapefiles. As a bonus, both platforms are compatible with AutoCAD formats such as .dxf, which can be edited and converted to shapefiles. 

It will correct geospatial errors and identify ground control points for geo-referencing. Finally, it can provide you with nicely formatted maps, to add scales, distance bars and mark up the image to your business’ professional requirements.

You can also create professional quality maps in there respective print composers, adding logos, keys and legends, and annotating text. Don't forget to add your North Arrows and Scale Bars and make sure to check this brilliantly in-depth guide on how to make a maps in QGIS. 

 

 

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