![]() ![]() If your imagery has no spatial reference you may have to georeference it using the Georeferencing toolbar. You can change the projection of your raster data using the Project Raster tool. When you’re projecting data, you are changing the coordinate values and sometimes the shape of your image (due to the warping of the pixels to another location). aux.xml file that gets stored with your raster dataset containing the spatial reference information. You need to use the Define Projection tool, otherwise the coordinate defined in the world file may place the image in the incorrect location. For example, there are a number of raster dataset file formats that use an associated world file to define coordinate and pixel dimensions for the upper left corner of the raster dataset. When you define the projection you’re simply identifying the coordinate system that is used to place you data’s coordinates in the correct location. – Book: Lining Up Data in ArcGIS: A Guide to Map Projectionsĭefining a spatial reference (projection) for your data is not the same as projecting your data. – 2010 Developer Summit: Understanding & Using Geometry, Projections, and Spatial Reference Systems – Help topic: Georeferencing and coordinate systems – Mapping Center: Map Projection Animations – Training: Understanding Map Projections and Coordinate Systems If you’re asking “What is a spatial reference?” then you should start with some of these other options: Spatial reference, projection, coordinate system? – I don’t know the spatial reference for my data. – The spatial reference exists but the data appears in the wrong location. – I know the spatial reference information but how do I apply it to the data? However, people are still dealing with issues of not knowing the spatial reference for some of their data, which includes imagery. ![]() There’s a lot of geographic data out there and most of it was created using a spatial reference. ![]()
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