Hawth's Analysis Tools for ArcGIS
CALCULATE MOVEMENT PARAMETERS (SIMPLE)
Input: a point layer representing consecutive locations (e.g. telemetry data)
Output: movement parameters are added to the attribute table: STEP LENGTH, TURN ANGLE, BEARING, NET DISPLACEMENT
- [NOTE: this tool formerly calculated Net Squared Displacement, but now calculated Net Displacement as this is easier to interpret than the squared value]
- the point file can contain multiple paths provided that individual paths can be distinguished using an attribute field coded with integers (i.e.
a unique integer for each individual)
- automatically calculates all four movement parameters in four fields called: STEPLENGTH, TURNANGLE, BEARING, NETDISP
- a NoData value of -999 is written whenever a parameter cannot be calculated (e.g. a turn angle for the very first record)
- STEPLENGTH: the distance between the current point and the next one in the data set (i.e. N, and N+1, where N is the current record)
- TURNANGLE: the absolute angle between the previous step and the next step (i.e. the angle between points N-1, N, and N+1)
- BEARING: the true bearing in degress of the line that connects the current point with the next point (i.e. N and N+1)
- NETDISP: the distance between the very first record in the path (for that individual) and the current record
- this program is very fast
- the point layer MUST be in a projected coordinate system (this tool
will not produce logical results if a geographic coordinate system is used)
- the records MUST be pre-sorted chronologically (by path, then by time) otherwise the tool will produce nonsensical results
- this tool is designed to work with shapefiles, other formats have not been tested
- this tool is a grossly simplified version of a much more sophisticated tool currently under development
- you MUST remember that -999 is the NoData value and should be
eliminated before generating summary statistics on these fields!!!
[Click for larger view]
A point layer must be loaded into ArcMap in order to use this
tool (i.e. a point layer that represents consecutive path locations that are already PRESORTED (by path, and the chronologically within paths). If your layer is not presorted in this manner (e.g. commonly the case for VHF data) then you should move your data to a program like Excel, and sort the data (first sort field: path / animal ID, second sort field: date, third sort field: time if applicable). If your point file does not contain an integer field that distniguished between multiple paths/individuals, then you need to create one before using this tool (e.g. if your path/animals codes are text based, you need to add a new field that is purely integer based).
This tool forces you to use the following field names for the movement parameters:
STEPLENGTH, TURNANGLE, BEARING, NETDISP. If any of those fields already exist
you will need to save that data in another field with a different name if you wish to use
this tool. The user is prompted to confirm whether any existing fields should be overwritten - if the user declines, the tool stops and no data is lost.