Image resolutions
The Pima County MapGuide server stores several pre-sampled image resolutions for each orthophoto layer. For instance, for the PAG 1998 grayscale orthophotos,the server stores seven pre-sampled panchromatic grayscale image resolutions from 64 foot pixels all the way down to 1 foot pixels. The server selects the data for your current view from image files with the most appropriate resolution as follows:
| 0-200 |
6 inch (where available) |
| 201-3,000 |
1 foot |
| 3,001-5,000 |
2 foot |
| 5,001-12,000 |
4 foot |
| 12,001-30,000 |
8 foot |
| 30,001-50,000 |
16 foot |
| 50,001-100,000 |
32 foot |
| 100,001-1,500,000 |
64 foot |
The MapGuide server re-samples the image on-the-fly, resulting in the smallest possible data transfers at all viewing scales. If the change in scale is small, the image may be re-displayed at the new scale without being re-sampled on the server. You can force a re-sample at the current scale by right-clicking on the imagery layer name in the MapGuide legend and select "Rebuild". For more on getting the best possible image to view, see Optimizing Orthophotos, Imagery and Map Details.
The MapGuide server manages selecting the displayed data from a large number of photo data tiles, stitches it together when necessary, and presents it to the user, making it appear as one giant seamless image. The intensive processing is done on the server, not your PC, and generally takes a few seconds for each new view.
Capturing the Data in Your MapGuide View
See Capturing Your MapGuide View to learn how to save the viewed map data from the screen to a file.