Each GCD project contains a survey library. Conceptually, the GCD considers each DEM to be a separate "survey". and theAdd Survey
Edit Existing Survey
Remove Existing Survey
Surveys successfully added in the survey library will be available for subsequent change detection analysis.
It is important to realize that the main reason the survey library exists is to help you organize your data for change detection analyses and enforce some of the best practices (e.g. orthogonality) required to do subsequent analyses. As such, the survey library makes a copy of all data loaded into the project, and organizes this in the input folder of the project.
You should create each new project in a separate folder. Do not store multiple GCD projects in the same folder.
These three functions are organized onto three different tabs of the
Note, if your rasters do not meet the GCD's dimensional divisibility and orthognality criteria, you will be prompted to fix them.
Associated surfaces are rasters that represent additional information about your survey. They are used in the calculation of error rasters. Common associated surfaces are slope or point density. Each associated surface is represented as a single raster dataset.
This video shows you how to add associated surfaces to your survey.
Each survey can have multiple error calculation rasters. There are four types of error rasters in the GCD:
This video shows how you can create a uniform error raster:
This video shows how you can load a user defined error raster:
This video shows how you can calculate an FIS error raster using a pre-loaded FIS and associated surfaces as inputs:
For more information on fuzzy inference systems and how they can be used to calculate elevation uncertainty surfaces, see here.