The orthoimagery in this image service was taken on 9/24/1974 over Harrisonburg, VA. Data was supplied from James Madison University. Dr. Glen Gustafson's ISAT Applied GIS Lab created this mosaic for the City of Harrisonburg from scanned prints. The dataset's coordinate system is WGS 1984 Web Mercator (Auxiliary Sphere). A cache was built using the the ArcGIS Online/Bing Maps/Google Maps tiling scheme containing 11 levels ranging from 1:288,895 to 1:282.

Metadata from JMU Student:

Dan Williams - March 22, 2004

Geog385 - Orthocorrected Mosaic

The assignment parameters consisted of mosaicking Harrisonburg, VA, September 24, 1974 Aerial photographs exposures 87 and 88. These photos had been orthocorrected in a previous assignment. I began my operations with a quality control check of the provided data.I was immediately unsatisfied with the results of mosaicking initials MSC's (exposure 87) output IMAGINE Image (.img) and my output .img (exposure 88) files from the previous orthophoto project. The photos were not aligned properly; the cause being differing orthocorrection results, and the visual quality was not consistent across both images. Perusing the files, I examined file sizes and recognized MSC's output .img was 32 megabytes (MB) and my output .img was 45.3 MB. After further investigation I learned that his resample pixel size was 1.75 meters and my resample pixel size was 1.5 meters. Looking at JG's data (exposure 87), I came to the conclusion that I did not have a good input image for exposure 87. JG's output image had very poor quality and it was 62.2 MB in size! Scrutinizing JG's output image, I learned that the image quality was poor due to the fact that his resampling method was probably 'nearest neighbor' and his file was unnecessarily big because his output pixel size was 1.25 meters. I made the decision to see if I could get better results by reprocessing the orthocorrection process for exposure 87. I first tried MSC's data, but was unable to copy his input data because of file naming/network conflicts. Therefore I used JG's data, but this time correcting his mistakes: using 'bilinear interpolation' for the resampling method and setting the output pixel size to 1.5, matching exposure 88. This produced much more desirable results. The best alignment was obtained by putting 87 over 88 in order. My computed active area had a crop area of 30%. Alignment and visual quality (i.e. brightness/contrast) of my output image was not flawless. I think better results could be obtained by completing the process individually from start to finish. I left my final mosaicked output image uncropped per Dr. Gustafson's instructions.

The orthoimagery in this image service was taken on 9/24/1974 over Harrisonburg, VA. Data was supplied from James Madison University. Dr. Glen Gustafson's ISAT Applied GIS Lab created this mosaic for the City of Harrisonburg from scanned prints. The dataset's coordinate system is WGS 1984 Web Mercator (Auxiliary Sphere). A cache was built using the the ArcGIS Online/Bing Maps/Google Maps tiling scheme containing 11 levels ranging from 1:288,895 to 1:282.

Metadata from JMU Student:

Dan Williams - March 22, 2004

Geog385 - Orthocorrected Mosaic

The assignment parameters consisted of mosaicking Harrisonburg, VA, September 24, 1974 Aerial photographs exposures 87 and 88. These photos had been orthocorrected in a previous assignment. I began my operations with a quality control check of the provided data.I was immediately unsatisfied with the results of mosaicking initials MSC's (exposure 87) output IMAGINE Image (.img) and my output .img (exposure 88) files from the previous orthophoto project. The photos were not aligned properly; the cause being differing orthocorrection results, and the visual quality was not consistent across both images. Perusing the files, I examined file sizes and recognized MSC's output .img was 32 megabytes (MB) and my output .img was 45.3 MB. After further investigation I learned that his resample pixel size was 1.75 meters and my resample pixel size was 1.5 meters. Looking at JG's data (exposure 87), I came to the conclusion that I did not have a good input image for exposure 87. JG's output image had very poor quality and it was 62.2 MB in size! Scrutinizing JG's output image, I learned that the image quality was poor due to the fact that his resampling method was probably 'nearest neighbor' and his file was unnecessarily big because his output pixel size was 1.25 meters. I made the decision to see if I could get better results by reprocessing the orthocorrection process for exposure 87. I first tried MSC's data, but was unable to copy his input data because of file naming/network conflicts. Therefore I used JG's data, but this time correcting his mistakes: using 'bilinear interpolation' for the resampling method and setting the output pixel size to 1.5, matching exposure 88. This produced much more desirable results. The best alignment was obtained by putting 87 over 88 in order. My computed active area had a crop area of 30%. Alignment and visual quality (i.e. brightness/contrast) of my output image was not flawless. I think better results could be obtained by completing the process individually from start to finish. I left my final mosaicked output image uncropped per Dr. Gustafson's instructions.