Monday, June 30, 2025

Introduction to G.Projector 3 — A Map Projection Explorer by NASA

 National Aeronautics and Space Administration (NASA) has this great tool called G.Projector for exploring complex Map Projection not easily implemented in common cartographic or GIS tool. The software is based o Java and it is available on major operating system like Windows, macOS and Linux. G.Projector is an interactive tool for exploring map projections. It takes an input map image, typically in Equirectangular form (also called Cylindrical Equidistant), and transforms it to one of over 200 other projections.


Download and launch G.Projector from the official website, it is a simple standalone software (no installation is required), however you need to have Java 11 or higher installed on your machine.

To start using G.Projector, you need to have a basemap (source map) of the globe in one of the following projections namely: Aitoff, Cylindrical equal Area, Equirectangular, Hammer, Robinson, or Winkel Tripel. Your source map in any of the projections above can then be transformed to one of over 200 other projections. An important note is that your input map image, must not have a border or extra margins around the edges.

A KMZ file ca also be used as an input source map.

With this tool, you can take a globe map like the once below and convert them into many types of map projections.






The steps required are as follow;-

1) Launch the G.Projector software

2) Go to "File" >> "New with import…", select your base map and choose its corresponding map projection such as "Equiretangular" as "Input projection"


3) In the "Projection" tab, select the new map projection type you want to transform the map into. As an example, here I choose "Sinusoidal" as projection mode with Interrupted: 30° Gores

4) In the "Graticule" tab, set the "Stroke" as you want

5) In the "Overlays" tab, select <None> for "Overlay 1".

6) In the "Border" tab, set "Weight" to 0%.

7) Export the current view now under "File" >> "Save Map as…"


A note on Gore
In cartography, a gore is a wedge-shaped segment of a map, often resembling the area between two lines of longitude, that can be fitted to a globe with minimal distortion. It can also refer to a triangular piece of land resulting from conflicting surveys or a gap between boundaries. 

1. Globe Gores:
A gore is a section of a map designed to be wrapped around a globe. 
These sections are typically shaped like a wedge, with the wider end at the top (near the equator) and the narrower end at the bottom (near the pole). 
The term "gore" in this context comes from the shape of the segment, which is similar to the panels of a hot air balloon or parachute. 

2. Land Gores:
In surveying and land ownership, a gore refers to a small, usually triangular, piece of land that is not included in any adjacent property or land survey.
These gaps can arise from errors in surveying, where two or more surveys fail to align properly, or from discrepancies in boundaries.
For example, the "g<bos> land" between the Philipse Patent and the Rombout Patent in New York was a well-known gore. 

3. Distinguishing Gores from Gaps:
While both gores and gaps represent areas not included in adjacent properties, a gore is generally triangular in shape, while a gap can be any irregular shape.
Gores often arise from conflicting survey lines, whereas gaps may result from errors in descriptions of property boundaries. 

That is it!

Happy Map Projection

No comments:

Post a Comment