Georeferencing
Raster data is obtained from many sources, such as satellite images, aerial cameras, and scanned maps. Unlike modern satellite images and aerial cameras that tend to have relatively accurate location information and might need only slight adjustments to line up all your GIS data, scanned maps and historical data usually do not contain any spatial reference information. In these cases you need to use the process of georeferencing.
Georeferencing is the process of assigning real-world geographic coordinates to a raster image or a scanned map, enabling it to be accurately placed within a spatial reference system. This process involves matching identifiable points on the image with corresponding locations on a reference dataset, such as a satellite image or a vector map. Georeferencing is essential in cartography and GIS, as it allows historical maps, aerial photographs, or other spatial data to be integrated with modern geographic information for analysis, visualization, and decision-making.
Resources:
Assignment 03
Urban development of the city
TASK:
Make a map showing the urban development of chosen city (your hometown, the capital of your country, ...). Derived the extent of built-up areas from old maps (try to show at least three time periods including this year). Try to quantify the change (in relative and absolute numbers).
In technical report answer following questions:
- How has the extent of built-up area changed during the whole time period (relatively and absolutely)?
DATA SOURCES:
SUBMISSION FORM:
- technical report + 1 map in PDF format (submit by 23/03, send to petra.justova@fsv.cvut.cz)
INSTRUCTIONS:
Step 1: Find a map
- Search the browser or digital map collections to find the old map of your chosen city
(If you find an already georeferenced map that is provided as a WMS/WMTS, connect it to ArcGIS Pro (1). and proceed to step 3)
Step 2: Georeference the map
- Add the old map to your Map project.
- Set the projection of Map properly (Properties-Coordinate Systems)
- Activate the Georeference tool (Imagery tab).
- Zoom in to the area of interest (area covered by the old map). Save the map display to Bookmarks (Map tab).
- On the Georeference tab choose Fit to Display to reposition and place the image within the current map display. You can use Move/Scale/Rotate tool to refine the approximate placement of the image for better identification of control points for georeferencing in next step.
- On the Georeference tab, click Add Control Points. Now try to find at least 4 identical points (control points) on the image (source) and the reference map (target). These points should be spread out throughout the image to obtain the best possible registration.
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After collecting all points, on the Georeference tab, click Save.
Step 3: Vectorization
- Create new feature class (Catalog-Databases-New-Feature Class). Choose the feature geometry, add fields for attributes you want to record (“year”) and choose the right coordinate system.
- Vectorize the extent of built-up area for all georeferenced maps (Edit-Features-Create Feature). For each polygon, i.e. an old map, enter the value for “year” attribute.
- Symbolize the layer properly to show the urban expansion of your city (Symbology-Graduated Colors). Overlay the layers on a reference map that reflects the current extent of built-up area (Map-Layer-Basemap).
- Finish the layout: insert Map Title, Scale, Legend and Credits. Feel free to make it nice! You can see an inspiration for your output below.
- Export Layout in PDF Format
Add WMS/WMTS service to ArcGIS Pro
