- Since these ortho images create large files,
each borough has been grided so that you only need to download and work
with those grids that cover the area you are interested in.
- The index files that display the grids, for the "Blue Sky" Orthoimagery for NYC are stored in D:\EDS\GIS\new_york\nyc_orthophoto.
- For each borough there are two layers: the imagery layer (.ecw) and the grid layer (.shp). Open both using the Add Data option in ArcMap.
- Make the grid layer hollow so that you can see the imagery layer beneath the grid lines.
- Zoom in to the area that you need to download.
- You need to record the image IDs for each grid that you wish to download. To do this you can turn on the label for the IMG_ID field and zoom in so you can read the label or you can use the information icon to display all the attribute values for a grid.
- The files for the individual grids are on the Blue Sky DVD which is stored in the cage with the other frequently used CD/DVDs. There are two files for each grid (.jpw and .jpg). Copy the pairs of files for each grid that you need from the DVD to your workspace in MyDocs.
- Open ArcCatalog and navigate the grid layers in your work folder for the purpose of applying the correct spatial reference to your files
- For each grid layer, open the layer properties (right click on the layer name), scroll down and highlight "Spatial Reference," click on the Edit button, click on IMPORT, navigate back to the borough .ecw file in D:\EDS\GIS\new_york\nyc_orthophoto, click on it, click ok, and then, in the Source window, click apply.
- You can now open the grids you selected in ArcMap. When prompted, you do not need to build pyramid layers.
