[017] Global Mapper - Elevation Layer 01

In the last post, I shared a script related to Python, but there were some layer-related functions I hadn't mentioned yet. While we're on the subject, I'd like to take a look at some frequently used features.

Global Mapper categorizes layer types into five main groups: Elevation (Terrain), Image (Raster), Point, Line, and Area (Polygon). The sub-items visible in the Layer menu change depending on the type of layer selected.

There are other types of layers, but I don't think many Global Mapper users will need to go that deep, so I won't be covering them here.

Let's start with the Elevation Layer.

One important thing to keep in mind is that Elevation Layers can be visually changed to represent slope or aspect simply by changing the Shader.

Therefore, the functions we are about to discuss can be used consistently even if the shader is changed. You can download and open the sample .gmp file below to follow along.

Attachment: Layer_Management.zip (This is a safe proprietary data file for Global Mapper.)

Looking at the layers registered in the Control Center, you'll notice that the icon to the left of the layer name changes based on the elements the layer contains (Terrain, Raster, Point, Line, or Area).

If you select a layer and right-click, a context menu appears. At the very bottom, you will see the Layer item. The sub-items under this menu vary depending on the layer type.

Since we are only dealing with Elevation Layers today, let's look at the context menu specific to them.

Brief Overview of Items:

1. Create Workspace File from Selected Layer(s)...: Saves the selected layer as a Workspace file (.gmw).
2. EXPORT - Export Layer(s) to New File...: Exports the selected layer to a new file format.
3. MAP CATALOG - Add Selected Layer(s) to Map Catalog...: Adds the layer to a Map Catalog (useful for massive, national-scale datasets).
4. BBOX/COVERAGES - Create Layer Coverage Box/Polygon Area Features: Generates a bounding box that encompasses all elements in the layer.
5. Create Point Cloud from Elevation Layer: Converts elevation data into a Point Cloud.
6. Create Area Features from Equal Values...: Creates polygons based on identical elevation values.
7. Vectorize Raster: Converts data into vectors (lines or polygons) based on threshold values.
8. Create Mesh Features from Terrain...: Generates mesh features based on terrain data (a preliminary step for creating TIN models).
9. Find Extreme (Min/Max) Elevation Values...: Searches for the minimum and maximum elevation values within the layer.
10. Link External Metadata File: Connects the layer with external metadata (XML, TXT, etc.).
11. Save List of Layers to Text File...: Saves the current project's layer list as a text file.
12. Set Background Color for Layer in Control Center: Sets a custom background color for the layer entry in the Control Center.

Items 1, 2, 3, 10, 11, and 12 are fairly self-explanatory, so let's explore the remaining functions. BBOX/COVERAGES is a common feature used across all layer types, not just Elevation. It creates a rectangular or polygonal border that contains every element in the selected layer.

When you select BBOX, a window appears asking you to select the layers. Select "Elevation" and click OK. Then, it asks whether you want a rectangular bounding area or a polygonal coverage area.

Choosing "Yes" creates the smallest possible rectangle containing all elements. "No" creates a polygon that fits the actual shape of the data more closely. In the example, a new layer called Elevation (Bounds) is created.

Next, let's try creating a polygon around a Point layer using the "No" (Polygonal) option. A Concave Hull Options window will appear, allowing you to set the "Smoothing" factor. Higher smoothing hides imperfections, while lower values cling more tightly to the data boundary.

Creating a Point Cloud

Now, let's look at Create Point Cloud from Elevation Layer. This function converts DEM (Digital Elevation Model) data into individual points, each containing an elevation value.

Personally, I wish there were a function to adjust the density of the generated points, but that option isn't available here. Once you click OK, an Elevation Points layer is created. In my test, it generated 44,290 features.

 If you turn off the DEM layer and zoom in, you can see the individual points. By using the Feature Info Tool (Alt+P) and clicking on a point, you can verify its specific attributes, including its precise elevation.

That's all for today...