Vessel position not correct
gallo
Global Mapper User
Hallo!
I am working in Iceland and I am using GM on a portable Yuma machine. Yuma has a virtual gps which is connected with GM. I open my aerial photos and project them as suggested using Isnet 93 projection. The coordinate in GM are correct but 1) the position of the vessel and the following tracklog are in the wrong position ( circa 15 m west). 2) I saved my tracklog as dgn microstation vector file, I imported it but its position is totally wrong, much more wrong then the position it was tracked in GM ( circa 500 km north-east). How can I fix these problems? Thanks
I am working in Iceland and I am using GM on a portable Yuma machine. Yuma has a virtual gps which is connected with GM. I open my aerial photos and project them as suggested using Isnet 93 projection. The coordinate in GM are correct but 1) the position of the vessel and the following tracklog are in the wrong position ( circa 15 m west). 2) I saved my tracklog as dgn microstation vector file, I imported it but its position is totally wrong, much more wrong then the position it was tracked in GM ( circa 500 km north-east). How can I fix these problems? Thanks
Comments
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These sounds like projection/datum issues. If you load in an independent source of data using the File->Download Online Imagery/Data menu command (perhaps the World Imagery or DigitalGlobe source) is the aerial imagery projected to Isnet 93 or the vessel data properly aligned? This step helps determine whether it's the vessel position or the aerial photos that's wrong. I would almost suspect the projection selection for the aerial photos is not correct so they are shifted.
For the DGN, is the position incorrect in GM or in some other software? Are you saving a PRJ file when you save the DGN?
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
Thanks! I agree but I find strange that the coordinates of a random point in the areal photo selected with the information pointer are correct. Anyway I tried as u suggested to load the jpeg2000 photo on the world imagery but pup up a message Warning no command found to process in script file.global_mapper wrote: »These sounds like projection/datum issues. If you load in an independent source of data using the File->Download Online Imagery/Data menu command (perhaps the World Imagery or DigitalGlobe source) is the aerial imagery projected to Isnet 93 or the vessel data properly aligned? This step helps determine whether it's the vessel position or the aerial photos that's wrong. I would almost suspect the projection selection for the aerial photos is not correct so they are shifted.
For the DGN, is the position incorrect in GM or in some other software? Are you saving a PRJ file when you save the DGN?
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
If the view projection is set to the native projection for the layer but that is not correct, the grid coordinates (the middle box on status bar) would be correct but the lat/lon associated with it (one to right) would be incorrect. When are you getting the error about the 'No command to process'? It sounds like maybe you are using the File->Load Workspace command rather than File->Open Data File to load the image?
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
Dear Mike, I tried to open my data file over the world imagery of GM but cannot distinguish which between the vessel or the areal photo are in the wrong position. But I can see that the coordinates of the virtual gps (in the yuma) and the coordinates in the gps information window correspond ( the vessel is connected with it) while the coordinates in the status bar don't. Then the 2 types of coordinates seems to fit between each other for a point in the areal photo. Do this tell u something?
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What are the 2 coordinate systems that you are using? What shows on the Projection tab of the Configuration dialog and what are you choosing for the aerial image when you load it? Does your imagery align with the World Imagery source? If not that would mean that likely the wrong projection or more likely datum (for small shifts) is being selected when loading the aerial imagery.
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
Hallo Mike! I believe I was using only one coordinate system! when I open my areal photo as instruction says I load from file the isn93 projection I had, in the configuration dialog appear Lambert conformal conic as projection and wgs84 as datum. Yes my aerel photo allign fairly well with the world imagery source. I tried to change datum, I selected the ISN93 (Iceland) but nothing change. I was wondering if is the virtual gps set in another unit system but I cannot see it.
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The ISN93 (Iceland) datum is basically identical to WGS84, so there wouldn't be any shift between them. The vessel data from the GPS should be in WGS84 and be automatically handled. Can you provide your saved GPS tracklog and the imagery and I can take a look and see what the projection/datum should be?
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
Hallo, regarding making a dgn file; u ask me: is the position incorrect in GM or in some other software? Are you saving a PRJ file when you save the DGN?
My answer are; the position are incorrect in microstation and my main problem is that I do not see the file ! I try to save the prj file but the problem is still there...thanks -
Microstation likely won't have nearly the projection support that Global Mapper has, so just the existence of a PRJ file won't mean anything to Microstation. What is your projection set as in Microstation? You will likely have to export into the same coordinate system from Global Mapper to get your data to display together in that software.
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
Hallo Mike,
when I export the dgn vector file GM tell me "All data will be exported using the currently select display...." this projection should be the same as in the "Configureas in microstation as I opened the same geotiff images automatically in both GIS without selecting a projection.THANKS -
What is the projection that you have set though? What does Microstation list as the projection? You will likely need to match the projection in Global Mapper when you export with the projection in Microstation to get your files to overlay as Microstation likely doesn't do any reprojection.
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com
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