CUBIZEN: Global Mapper, CityEngine & Creative Tech

When you use online maps in Global Mapper, there is one significant drawback: every time you pan or zoom, the software has to connect to the map server to reload the area. This can quickly become frustrating and inefficient during GIS work. In such cases, you can convert the map for offline use. By loading locally saved imagery instead of reconnecting to the server each time, you can significantly improve navigation speed and workflow efficiency.

Why Offline Maps Improve Performance in Global Mapper

Video demonstration of the online map export workflow in Global Mapper.

Let's get started.

Step 1: Loading Your Workspace

First, open the workspace you saved in the previous session.

Step 2: Checking the Loading Lag

On this screen, try zooming in while keeping all layers off except for World Imagery.

Tip: You can zoom in and out using the mouse wheel, and pan by clicking and dragging with the mouse wheel button.

Notice how the map reloads every time you zoom or pan across a new area. If you zoom in beyond the screen size and pan, you'll see that it takes time to load new areas as well. This happens because the imagery is streamed dynamically from an external map server instead of being cached locally on your computer.

Step 3: Exporting Online Maps as Offline Raster Files

Now, let's export the online imagery as a local offline raster file.

1. Select the World Imagery layer in the Control Center.
2. Right-click and select Layer - EXPORT.

When the "Select Export Format" window appears, choose JPG and click OK. (You can select other formats depending on your specific needs.)

Step 4: Choosing Resolution and Metadata Settings

When the JPG Export Options window appears, configure the settings as shown below and click OK.

Understanding Sample Spacing and Export Resolution

Sample Spacing: This defines how many meters represent one pixel.

• For example, if you enter 1, 1, then 1x1m of the online map becomes 1 pixel.
• If you enter 5, 5, then 5x5m of the online map is saved as 1 pixel.

The smaller the number, the higher the resolution, but the file size will be larger and downloading will take longer. Since World Imagery uses an international server, setting it to 1x1 might take 3-4 minutes or more for the current map. (Using V-World API is much faster, often taking less than a minute. I highly recommend applying for and using the V-World API.)

Why JGW and PRJ Metadata Files Matter

Metadata File Formats to Generate: Make sure to select World File (.jgw) and PRJ (Projection) File. Since standard JPG files do not store geographic coordinate information, GIS programs use these JGW and PRJ files to place the image in the correct coordinates.

Step 5: Saving the File

Choose your save location, enter a name, and click OK.

A progress bar will display the download and export process. Once finished, the window will disappear.

Step 6: Loading the Offline Map

Now, let's load the map we just saved. Go to File - Open Data File(s)...

Select the JPG image from the location where you just saved it and click OK.

You will now see the "Offline Map" (오프맵) added to the bottom of your Control Center.

Conclusion: Optimizing Offline Map Quality and Performance

Now, try turning off the original World Imagery layer. Since we downloaded it at a lower resolution this time, the imagery may appear blurry when viewed beyond the exported resolution. However, if you zoom in, zoom out, or pan, you'll notice that the screen transitions at a much faster speed than before.

The map used in this example is about 6x6km. If you download it at 1x1m resolution, it becomes a 6,000 x 6,000-pixel image, which is quite large. Higher resolution increases visual quality, but it also increases export time, storage size, and rendering overhead. It is best to download at an appropriate size, considering the final output size for your reports or projects.

That’s it for today!