Color orthophotography: To scan or not
Abstract
A picture is worth a thousand words, which explains why digital orthophotographs have become such a popular item. Today, most procurement of orthophotographs result in a digital product. However, if one already has hard copy orthophotography, should one scan them, or have them produced as true digital orthophotographs? What are the advantages and disadvantages of each methodology? This paper examines the procedure the Facility for Information Management, Analysis, and Display (FIMAD) at Los Alamos National Laboratory (LANL) uses to determine the appropriate product based on our needs. The scanned product is compared to a digitally produced orthophotograph, procured through a vendor. Comparison is performed on the screen, on hard copy output, and by spectral analysis in the red, green and blue bands. Full screen sized images look fairly good, but when enlarged, the scanned image appeared blocky and fuzzy. Hard copy output from the electrostatic plotter produces colors similar to the screen for the demo image, but renders poor color matching with the scanned image. Histograms of each band of the scanned image show a high count at the low end of the curve. These findings confirm that the images are different, and that the differences are not just in the eyes of the beholder. It was concluded true digital orthophotographs are needed.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- 1994
- Bibcode:
- 1994STIN...9524069B
- Keywords:
-
- Color;
- Digital Systems;
- Images;
- Orthophotography;
- Scanners;
- Scanning;
- Histograms;
- Image Processing;
- Spectrum Analysis;
- Instrumentation and Photography