These data layers are used to index the
2008/2009 USGS Color Ortho Imagery tiles and the DVD schemes used for their distribution. They are stored in ArcSDE as follows:
- COQ2008INDEX_POLY - 2008/2009 USGS Color Ortho Index (for GeoTIFF and MrSID 1,500m x 1,500m tiles)
- COQ2008MOSAICS15CM_POLY - 2008/2009 USGS Color Ortho MrSID 15cm Mosaics Index
- COQ2008MOSAICS30CM_POLY - 2008/2009 USGS Color Ortho MrSID 30cm Mosaics Index
PDF Index for more detail and as a reference when ordering or downloading the imagery.
The 1,500m x 1,500m tiles index polygons were created by using the Generate Fishnet command in ArcGIS 9.2 and converting the line layer to a polygon feature class. The origin of the fishnet was chosen such that the maximum amount of 2008 imagery was covered after projection from the UTM Zone 19N coordinate system to NAD83 Mass. State Plane Mainland Meters. Each polygon is 1,500m by 1,500 meters, insuring that the original 15cm and 30cm resolutions would be preserved in the projected imagery and be fully contained in each tile. The TILENAME attribute was populated by creating centroid points for each polygon, adding its XY state plane coordinate to the point (with the Add XY tool). A new attribute was added to the point layer comprising the first 4 digits of each X and Y coordinate. A spatial join transferred the 8-digit string to TILENAME in the polygon layer. Each polygon was then coded for resolution and which mosaic would include it, for each resolution. The Dissolve tool was used to create the MrSID indexes, using the MOSAIC15CM and MOSAIC30CM attributes.
Another layer, COQ2008MOSAICS15CMND_POLY, represents areas along the edges of some 15cm tiles where image data are not present. This layer may be used as a mask and was created by MassGIS because the 15cm imagery were delivered in the UTM coordinate system (2008) and Mass. State Plane Feet (2009), and when converted to Mass. State Plane Meters some rotation and resampling occurred; then, when clipped to the COQ2008INDEX_POLY layer some tiles were not completely filled with image data. See the image at right for an illustration.
The polygon attribute tables contains the following fields:
|Attribute||Description||Contained in Feature Class(es)|
|TILENAME||Unique 8-digit ID for each 1,500m x 1,500m tile||COQ2008INDEX_POLY|
|RESOLUT||Available resolution for the 1,500m x 1,500m tile:|
- 15cm and 30cm
- 30cm Only
|MOSAIC15CM||Name of MrSID mosaic comprising 15cm tiles|
|MOSAIC30CM||Name of MrSID mosaic comprising 30cm tiles||COQ2008INDEX_POLY|
|COQ2008||"Y" if flown in 2008, "N" if flown in 2009||COQ2008INDEX_POLY|
|COQ2009||"Y" if flown in 2009, "N" if flown in 2008||COQ2008INDEX_POLY|
These datalayers are maintained by MassGIS.
Last Updated 5/30/2013