RS: Geometric Transformation of Raster Images

First, get the shapefile (GIS vector layer) for Lower Passaic and Saddle Watershed Management Area 4 (WMA 4) 1995/97 Landuse/Landcover from The DEP site (Downloads, Data, by Watershed, 1995/97 Landuse/Landcover). Unzip the .zip file to create a folder w04lu95, with multiple files. This GIS layer will be your reference map. It is a VECTOR LAYER (shapefile). If the data are not easily retrievable from the DEP site, get the local copy. The file is w04lu95.zip. Extract the files in it to a new directory. Make a note of where you save the folder. Open the Shapefile in a Viewer (set the type to Shapefile in the drop-down at the bottom, then go look for the file, it will have the .shp extension). NOTE that shapefile GIS layers consist of several files: a .shp that contains the spatial data, a .dbf that contains the attribute table, and a few others (do not delete any!). Right-click inside the Viewer to scale the GIS vector map to the Viewer extent. Then click on the Metadata icon to bring up the metadata/coverage information tool and select Add coverage projections. Here you will set the map projection -- but what is it? To find out, either look at the METADATA link at the DEP page, or use this link to the local copy of the METADATA page (as you know, metadata is information about data). The Spatial Reference Information section will tell you the right map projection and zone number to use). To cheat on this stage: get the njsp83.prj file (or on the Layers by Watershed page), rename it w04lu95.prj (must match other files!), and put this in the w04lu95 folder with the other files. Second, get the RASTER IMAGE you will be correcting: click on the yellow IMAGE button on the DEP page (for Lower Passaic, Saddle WMA #4) and right mouse to save the image to file (be neat! put it in your w04lu95 folder). There is also a local copy shown below: The image above is just a picture: it cannot be used in a GIS or image processing package as it does not have map or projection information BUT more importantly, it could be warped. You are now going to 'warp' (geometrically transform) this image to produce a 'geo-referenced' raster image, i.e., an image that is referenced to the Earth. Note: The minimum number of GCPs is necessary to calculate the transformation -- depending on the order of the transformation -- is: The Vector Viewing Properties tool allows you to change the way that vector data are displayed. For example, polygons can be displayed filled (with solid color or patterns), or just as outlines (i.e., only the perimeter is displayed). This can be important if you want to visualize existing vector GIS map layers over a land cover map obtained via classification of RS imagery -- as in this assignment. What are the differences between the various output images? Please examine them and comment: were you able to figure out why they are different? Source.


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Last Modified: April 22, 2016 @ 12:03 pm