Buffer / Overlay module is a simple GIS module, this module allows you to generate Buffer from point, line or polygon data and perform Overlay operations between polygons with several options including Union, Intersection, Difference and Symmetrical Difference.


Buffer is a zone around point, line or polygon feature measured in units of distance (meters), buffer is usually used for proximity analysis such as approximately of flooding area around the river, noise analysis around the main road, etc.

In our APP, buffer is generated from existing data (point, line or polygon), so before generating buffer make sure you already have point data (Marker, get from Marker Map module) or line & polygon (register using this module or using Area/Distance Measure module) in your database. Buffers can be generated for all features at once or for selected objects by clicking on existing point, line or polygon on the map and follow the instruction. Buffer length units are meters and cannot be empty.

For polygon features, buffer length can be set as negative number, it means that generated buffer will be smaller than input polygon.

Variable Buffer

Buffers can be generated with fix or variable length, it means each features can have different buffer length. For variable buffer, the buffer length will be taken from the notes attribute at each point, line or polygon. Make sure each data has a note and should be decimal number in meter units.

Dissolve Overlap Buffer

There is an option to merge overlapped buffers called Dissolve Buffer as illustrated below (image source: ArcGIS):


Overlay is a GIS operation that superimposes multiple data sets (representing different themes) together for the purpose of identifying relationships between them, in our APP overlay can be perform in different methods including Union, Intersection, Difference and Symmetrical Difference as illustrated below (image source: QGIS):


This algorithm checks overlaps between features within the Input layer and create new feature that contain polygons representing the geometric union of all the inputs.


This algorithm will create a new polygon that contain the overlapping portions of two overlapping polygons features.


This algorithm extracts features from the Input layer that fall outside features in the Overlay layer. Input layer features that partially overlap feature in the Overlay layer are split along those features boundary and only the portions outside the Overlay layer features are retained.

Symmetrical Difference

This algorithm extracts the portions of features from both the overlay polygons that do not overlap, overlapping areas between the two polygons are removed.