March 8, 2021

GeoTalks Express Bathymetric Analysis in Global Mapper Questions

Thank you for attending GeoTalks Express. The recording for this session have been posted and as a registered attendee you should have received an email with links to view them.

If we have a license for v22.0, do we need a new license for 22.1?

With the release of Global Mapper version 22.1 users with active Maintenance and Support on their license can download, install, and register the new version of the program. 

Link to download Global Mapper:

If you have a single user or single floating license, you will be prompted to register Global Mapper v22.1 by entering your Blue Marble login info and full order number. 

For dongle or network license types, or if you have questions about your order status, please contact our licensing team at 

How can you merge topo maps with BSB nav charts?

Raster image or chart layer can be superimposed over terrain data. Loading both data types into a workspace and layering them so the image/chart layers appear on top, you can open the 3D viewer and see the images textured by the terrain data. 

To apply some hillshade texture to the charts in the 2D view, load both data types and again layer them so the image/chart layers appear on top. Next, open the layer display options for the image/chart layers and select a blend mode or check the option to texture map. 

How can I do work using HDF5 data in Global Mapper? How can I manage to upload, visualize and process HDF5 data?

​HDF5 file types are supported in Global Mapper. When loading HDF5 files you can select an existing definition or create a new definition to load the file. More information on HDF5 file support and import can be found here in the Global Mapper knowledgebase

Can you use the slope as well as the heights for the seamount detection?

Peaks and depressions in a dataset can be identified using the contour generation tool. This process uses the contours generated at a user-specified interval to identify high and low points by counting concentric closed contour lines. There is no method in this tool to use slope values from the elevation data layer. 

Outside of the contour generation tool you can color elevation data by the slope values and use the slope measure in other analysis processes. 

Is this an xyz file? How do you interpolate?

The ASCII Grid (*.asc) file format, like the one shown in the webinar, will load into Global Mapper as a gridded elevation surface. If you do have an elevation file that loads as point features with associated elevations, you can create an elevation grid from these points in the Global Mapper program. 

Is it possible to plot the cross-sections?

Yes, after creating the cross-section views with the Path Profile tool you can use various options from the File menu in the Path Profile dialog to save the cross-section. The option to Save Path to New Layer will add a layer to your workspace containing the cross-section as a 3D line feature. 

Is the bathymetry data always a negative or can we set down as positive?

In the layer options for a layer of elevation data, you have tions to Alter Elevation Values. Here you can specify a scale factor, like -1, to flip the data from positive values to negative values as needed. 

To merge Topo and Bathy we need to use a common vertical ref. Are we able to apply tide corrections to depth data to get to a reference surface?

In the layer options for elevation data you can apply an elevation offset value to a layer of elevation data in the Alter Elevation Values tab. This may serve as one method to perform some tide corrections on your data. 

​Is there a way to buffer a line into a line instead of a line into an area?​

Features created with the buffer tool are by default area features, but in Global Mapper you can easily convert an area feature into a line. With the area selected move to the digitizer menu and select the option Advanced Feature Creation > Create Lines from Selected Areas. This option can also be found on the Digitizer Edit toolbar and will create a new line feature from the selected area. 

Can you re-project this to a different coordinate system?

Yes, data can be reprojected in Global Mapper by changing the workspace projection in Configuration > Projection. Any data exported from Global Mapper will be written out using the workspace projection specified in Configuration > Projection. 

Can you also assign elevation on points based on the surface?

You can apply elevation to any vector features from a loaded elevation grid layer. Select any features you would like to apply elevations to, then from the digitizer menu select Analysis/Measurement > Apply Elevations to Selected Features

Is it possible to create a grid by selecting how many points to use per m2? like 10 0r 20 points per m2?

Grid creation in Global Mapper will use all data points in the layer. If you have loaded the data as a point cloud, you can thin the point cloud layer to a more sparse dataset in order to use fewer returns when generating the elevation grid layer. 

The spacing parameter set in the grid creation dialog will determine the pixel size in the generated gridded elevation layer. 

Can spot soundings be created to go with the contours or by itself (Not just the shallowest and deepest value)?

With the contour generation tool you can identify the high and low points across the entire dataset, but you can also use the generated contours to identify local peaks and depressions. This option in the contour generation tool works to find local high and low spots by counting the concentric closed contours. 

If you have existing point features you can also apply elevations to these features from loaded terrain data. 

What does the grid interpolation value represent? Does 1 equal 1m gap in data?

The number associated with the Grid “No Data” Distance Criteria in the Grid Creation tool is the number of point spacings interpolated over when generating the grid. So for example if you had a point spacing of 0.5 meters, a  Grid “No Data” Distance Criteria value of 10 would interpolate over gaps in data 5 meters or smaller. 

I didn’t quite understand how you generated the dredged channel.

The workflow to create and dredge the channel involved a few different tools. To create a vector feature representing the channel a line was buffered to create an area feature. An elevation attribute was then added to this new area feature to give the channel bottom a consistent elevation. Once this feature was created with an elevation we returned to the original point data and created a new elevation grid layer using the point cloud and the channel vector feature with the option to Use 3D Area/Line Features as Breaklines. This created a layer that flattened the terrain of the channel to the elevation defined for the vector feature representing the channel. 

The track line that you suggest… how can we use it? I would like to imagine that it’s possible to use it on a trip…

If you have a GPS enabled device plugged in your computer, you can use Global Mapper to track where you are on a vessel. You first set up the GPS parameters in the Setup GPS menu. After that, you can use Start Tracking GPS to start showing the location on your screen.

Can you calculate the length of the 3d cable line?

If you draw a line feature across the terrain dataset, the next step is to split the line feature into segments. If you have an existing line segment, you can just split the line. It still remains 1 line feature, but vertices are inserted on the line feature, and then elevations are applied. You would select the line feature, then right click, go to Crop/Combine/Split Functions > and choose Resample/Split Features. We choose to Sample Features at a fixed distance interval. After that, select the line again, and go to Analysis/Measurement > Apply Elevations to Selected Features. You choose the terrain data set in the next window. Then select the line again, go to Analysis/Measurement and Add/Update the Measure Attributes. You can look at the 3D length using the Feature Info Tool. You can check out the Z values for each vertex by selecting the line, right click and go to Vertex Editing > Edit Feature Vertices.

How can we get the data you are working on?

While we don’t have the data we used packaged up for download all together, most of it was gathered from public data sources. These sources include the GEBCO data and NOAA.


So *.GSF files should be better converted to *.LAS/*.LAZ?

Global Mapper does support the import of GSF files. These files can be loaded into the program and worked with for analysis. When working with point cloud data LAZ and LAS formats are great options for exporting data as they are widely supported in many programs. 


You introduced adding custom symbols into the map. I need to do this along some transit lines with a boat model with a defined heading and position.  When I do this the symbol is not placed where it is defined as a coordinate (0,0).  I need help in getting this to work correctly because I get the symbol positioned relative to the defined position incorrectly.  How do I do this?

​Any custom symbol should be displayed as centered on the coordinate location of the point. If you select the point feature with the feature info tool where does the selected point appear in relation to the ​symbol being used?

​Any screenshots or further details on your workflow ​with these custom symbols may help us to better understand the challenges you are facing in Global Mapper. 

Companies using Blue Marble’s geospatial technology