GlobalMapper fills DTED file voids with data?
yigal
Global Mapper User
Hi,
I have a DTED level 1 file with some voids. When I review it with GlobalMapper (anti-aliasing is off) I can't see any empty spots, all the data looks OK. However when I review the DTED file using binary viewer I observe the voids. More than that when I export the data to GeoTIFF elevation file and open it with image viewer I'm able to see voids, but if I load the exported GeoTIFF to GlobalMapper the voids disapeared. So the question is the GlobalMapper fills the small voids automatically?
I have a DTED level 1 file with some voids. When I review it with GlobalMapper (anti-aliasing is off) I can't see any empty spots, all the data looks OK. However when I review the DTED file using binary viewer I observe the voids. More than that when I export the data to GeoTIFF elevation file and open it with image viewer I'm able to see voids, but if I load the exported GeoTIFF to GlobalMapper the voids disapeared. So the question is the GlobalMapper fills the small voids automatically?
Comments
-
That is strange, Global Mapper should not be automatically filling any voids during display. Can you send me (or post) the file so that I can take a look?
Thanks,
Mike
Global Mapper Support
support@globalmapper.com -
I'm sorry, my mistake. I forgot that DTED negative values are sign magnitude and in that particular file were "sea-level" zeroes 0x8000 which I, erroneously, consider as voids. However, the DTED-to-GeoTIFF export "supported" my mistake.As you can see, the white dots in attached file (JPEG converted from GeoTIFF) are at the places of those "negative zeroes" tracking coast line.
-
Can you send me the file in question so that I can take a look? I would expect a value of 0x8000 in the DTED file to just be zero and get output to the GeoTIFF file as such.
Thanks,
Mike
Global Mapper Support
support@globalmapper.com -
Sent to e-mail
-
I took a look and discovered that there are actually a bunch of true negative values near the shoreline (usually in the -1 to -4 meters range). When you export these to a 16-bit vertical GeoTIFF they are going to be written as normal 2s complement numbers, when would look like very large numbers if you treated the values as unsigned 16 bit values, like a application that interpreted the 16-bit GeoTIFF as an image rather than a series of gridded signed values would.
Let me know if I can be of further assistance.
Thanks,
Mike
Global Mapper Support
support@globalmapper.com
Categories
- 12.7K All Categories
- 5.6K Features Discussion
- 342 Downloading Imagery
- 1.3K Elevation Data
- 380 Georeferencing Imagery Discussion
- 628 GM Script Language
- 53 User Scripts
- 113 GPS Features
- 414 Projection Questions
- 819 Raster Data
- 1.3K Vector Data
- 6.6K Support
- 177 Announcement and News
- 908 Bug Report
- 558 SDK
- 1.2K Suggestion Box
- 3.7K Technical Support
- 562 Other Discussion
- 129 GIS Data Sources
- 27 Global Mapper Showcase
- 233 How I use Global Mapper
- 107 Global Mapper Forum Website