The following workflow uses the Black Mountain.gmw file that was saved at the end of the Accessing Online Data topic.
In the field of GIS, the most common function of raster data is to provide a visual and spatial context for vector mapping projects and the common characteristic of each of these datasets is that each of the pixels in the raster layer contains a color value, usually derived from a combination of red, green, and blue values (RGB).
In this section, we will explore some of the tools within Global Mapper that can be used to adjust the display of the pixels. We will begin by adjusting the color intensity of the imagery tiles that we have been using to accentuate the display of an overlying vector layer. We will then look at a couple of variations on the theme of applying transparency, and we will wrap up this section by blending the contents of overlapping raster layers together.
Adjusting the Color Intensity
- If necessary load the Black Mountain.gmw file from your My Maps folder.
- In the Control Center, uncheck all layers except for the Black Mountain Imagery layer group.
- Double-click on Black Moutain Imagery layer group in the Control Center to open the Raster Options dialog box. Opening the Raster Options dialog for a group allows you to apply display changes to all the layers contained in the group.
- In the Display tab, move the Color Intensity slider to the left until the corresponding value is approximately -120
- Click the Apply button to see the results applied to the imagery tiles.
Note that the Apply button can be used to preview the results of a setting while keeping the dialog box open to allow further adjustment. The OK button will apply the setting and close the dialog box.
- Click the OK button to close the Raster Options dialog box, and in the Control Center, turn on Black Mountain Parcels.shp layer.
Note that the property outlines are much easier to see against the more muted colors of the imagery.
- Reopen the Raster Options dialog box for the Black Mountain Imagery and click the Default button below the Color Intensity slider.
- Click the OK button to apply the display change and close the Raster Options dialog box.
We will continue to work with this data in the next section so you can leave the workspace open.
As with edits made to vector data, adjustments applied to raster layers in Global Mapper will be applied internally and will not be reflected in the external files.
Adjusting the Transparency of Raster Layers
By default, raster data is opaque and as a result, only the topmost raster layer will usually be visible. Adjusting the transparency of this layer will allow some of the details from an underlying layer to be displayed. In this exercise, we will explore some of the layer-specific tools and settings that can be used to visually merge raster layers together.
Follow along with this video demonstration and the instructor explores some of the raster display options. The workflow shown in this video begins with the Black Mountain workspace and creates a new Black Mountain Imagery workspace that will be used in subsequent workflows.
Imagery and other raster data are readily available online however it is a good idea to download the data as a local file before embarking on any raster processes. Working with locally stored files decreases load speeds and ensures access to the data in offline environments.
- The pixels in a raster layer store information in much the same way as the attribute table stores information about vector features.
- Global Mapper provides an array of tools for modifying the pixel values to adjust the display of the corresponding layers.
- When working with overlapping raster layers, there are numerous options for visualizing a combination of the two layers.
- Click here for more information on the raster layer display options available in Global Mapper.
Click on the Mark Complete or Next Topic button to learn more about Cropping Imagery.