BMSK File

What are BMSK files and how to open them

Are you having problems opening a BMSK file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your BMSK files.

What is a BMSK file?

A .BMSK file is a STK Body Mask Format file.

A STK Body Mask Format file holds definitions used by Analytical Graphics, Inc.'s Systems Tool Kit (STK) to limit a sensor's visibility by defining which directions are masked and which are allowed. It is used to describe exclusion or inclusion zones - parts of a full spherical view where a sensor should ignore certain areas or treat others as visible for access, line-of-sight, or coverage analyses.

The file is generated in STK when using the Body Mask or Az/El Mask tools. It is applied as an access constraint on Sensor objects, so that STK considers only those view directions allowed by the mask when computing sensor visibility, observability, or obstruction. The mask constrains the sensor's field of regard based on the geometry of obstructions or specified blocked angles.

Internally the format is ASCII text. It begins with a version stamp like "stk.v.<major>.<minor>" indicating the STK version from which it is valid. Keywords include inclusion and exclusion blocks, azimuth/elevation boundary pairs (NumAzElPairs), and orientation from the parent body frame defined via LocalX and LocalZ. Keywords such as CoordinateAxes, InterpolationMethod, and MaxAngleBetweenSamples refine how boundary sampling and axes alignments are handled. Markers such as BEGIN Inclusion/END Inclusion or BEGIN Exclusion/END Exclusion delimit zones.

How to open BMSK files

Important: Different programs may use files with the BMSK file extension for different purposes, so unless you are sure which format your BMSK file is, you may need to try a few different programs.

We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!

Last updated: August 24, 2026

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