Create sounding points over large area.
Dean Morrow
Global Mapper User
Hi, I've been using GM for last couple years and really love the program.
I have a question about creating points from a bathy grid. I'm building my own chart of the waters off the coast off Baja Mexico and would like to add some sounding points. Is there a way to create random or evenly spaced points with elevation attributes from the elevation grid? If not is there a way adjust the labels for the contours I have already generated so that they appear uniform? Maybe there is a way to have the label at a fixed degree to the chart view itself instead of the contour?
Thanks for the great program!
Dean
I have a question about creating points from a bathy grid. I'm building my own chart of the waters off the coast off Baja Mexico and would like to add some sounding points. Is there a way to create random or evenly spaced points with elevation attributes from the elevation grid? If not is there a way adjust the labels for the contours I have already generated so that they appear uniform? Maybe there is a way to have the label at a fixed degree to the chart view itself instead of the contour?
Thanks for the great program!
Dean
Comments
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Dean,
You can right-click on a layer in the Control Center and select to create points at the grid cell centers of a grid. Assuming you don't want the points quite so often, you could export the grid to a lower resolution (use a resampling method like Box Minimum 5x5 or something), then load it back in and create grid cell points from that layer. You would want box minimum for bathymetry so you get the deepest point at each location (or box maximum if you are making maps for ship traversal and care more about the minimum depth.
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
Okay that works! Thanks!
One other thing though. The native elevation values for my grid are in meters but when I export the points and use elevation as the label I get very large numbers. Is there a way to output or display them in meters or fathoms? -
How large are the numbers? I would expect the labels to show whatever the elevation was set to. Do they have extra digits of precision or something?
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
The numbers are 6 digits where they should be 4. Here is a screenshot that will give you a good idea of what I'm getting.
Dean -
Dean,
If you select one of those points what do the attributes look like? Those values look very odd to me.
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
Mike, here's a screenshot with the feature info and also I noticed for some reason the lower res grid I created opens with centimeters as the interpreted elevation units?
Thanks
Dean -
Dean,
What format did you export your lower resolution grid to? The Global Mapper Grid format would default to centimeters as it internally stores elevations as whole numbers to achieve the great compression. That could explain it if you are seeing centimeter versions of your data. You could fix this by exporting your lower resolution grid and making sure to select meters as the unit. Maybe export to a Float/Grid rather than Global Mapper Grid so you can get the full resolution without having to go to more precise units. Or you could right-click on the layer in the Control Center and select the CALC ATTR option, the multiply by 0.01. However I can't recall if that is in the version you have or not.
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
Mike, I exported to an ascii format at 15000 m resolution and it fixes the centimeter issue and the elevations display correctly for meters. The depth values are still kind of big and are in the format 0000.000 is there a way to covert the elevations to fathoms? Or at least remove the decimal numbers?
I'm using 12.02.
Thanks
Dean -
Dean,
If you are exporting to ASCII you could use the Point Offset/Scale to multiply your Z by the conversion factor from meters to fathoms (0.546806649), then the units will be that in the file. The latest build of Global Mapper also has a way to specify the number of digits of precision in the ASCII export right on the export dialog, but that isn't in v12.02.
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
Okay I'll try that method to convert to fathoms. Looks like I'll have to upgrade pretty soon.
Thanks for the help Mike!
Dean -
Mike,
I use an alternative program at the moment to reduce my ASCII data into points that I can plot on my charts. When I upload this reduced data in GM it doesn't appear to be located in the right location. (Berth Pockets).
How can I reduce my original ASCII data files (with millions of points) to (for example) one point in a 50m radius for each section whilst retaining the minimum depth (for safe navigation) for that particular section?
Also, can GM 14 merge seperate ASCII data files into one file?
Thanks
Frans -
Frans,
If you just have XYZ data, try exporting to a Lidar LAS file, then pull that in and select the Preview mode option which loads every 10th point. The upcoming v14.1 release in December will likely also have more point thinning options for point clouds, including keeping minimum elevation. Also if you have gridded the data, try setting the resampling method to one of the 'Box Minimum' options to reduce the resolution but keep the minimum elevation.
You can certainly merge multiple files. Just load them all, then use File->Export to export to a single new file.
Let me know if I can be of further assistance.
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
Thanks Mike,
Time difference between our countries comes in Handy.
Looking forward to V14.1, GM 14 is already a great tool with great and unprecedented support.
Frans -
global_mapper wrote: »Frans,
If you just have XYZ data, try exporting to a Lidar LAS file, then pull that in and select the Preview mode option which loads every 10th point. The upcoming v14.1 release in December will likely also have more point thinning options for point clouds, including keeping minimum elevation. Also if you have gridded the data, try setting the resampling method to one of the 'Box Minimum' options to reduce the resolution but keep the minimum elevation.
You can certainly merge multiple files. Just load them all, then use File->Export to export to a single new file.
Let me know if I can be of further assistance.
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com
Mike,
What would be the best option for thinning XYZ-data with GM version 15.1 ? What would be the best way to do this now?
Kind regards,
Danny Geysen -
Treating the XYZ data as Lidar will provide you with the most options for thinning the data. The data could be loaded as Lidar through the Open Generic ASCII text file option and selecting Lidar Point Cloud under Import Type. The data could also be exported into Lidar LAS format and re-imported. Loading the data as lidar, you will be presented with the Lidar load options dialog box where you can thin the data based on sampling or Standard deviation from the mean elevation value. Also, in the search dialog box, the data can be sorted or searched and thinned manually. The lidar module would provide more thinning options such as limiting the points to within a specific elevation range.
Thanks,
Cassandra -
o.k. Cassandra, thank you very much. That's working nice.
But now I would like to export to a CSV-file with the following format: LAT(decimal degrees),LON(decimal degrees),depth
example 51.70284616,4.492778166,10.38
What would be the best way?
Is it possible without a script?
-
Yes, that can be exported without a script. First, be sure that the data is projected in Geographic (Lat/Long) and change the Position Display Format to Decimal Degrees under the General tab in the Configuration Dialog box. Next, go to File> Export> Vector> CSV and be sure to check the box Format Lat/Long Coordinates with Position Display Format.
Thanks,
Cassandra
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