Frequently asked question

Why does the MOLE IGraphicDef.MinPointCount property return zero or not match the minimum points required by the military specification?

Last Published: April 25, 2020


The MOLE API communicates the required geometry type and minimum and maximum number of geometry points for a tactical graphic symbol ID/function code using the IGraphicDef and IGeometryLimits interfaces. These interfaces contain the following properties to perform this function:

Property - Helpstring:
IGraphicDef.ConstructionNotes - A human readable string/notes that describes how to build the core geometry for the graphic.
IGeometryLimits.GeometryType - The type of geometry (equivalent to esriGeometryType). MOLE supports the following types: 1 – Point, 3 – Line, 4 – Polygon.
IGeometryLimits.MinPointCount - The minimum number of points required. Default is 0 (use normal geometry limits).
IGeometryLimits.MaxPointCount - The maximum number of points required. Default is 0 (use normal geometry limits).

Some confusion can arise when MinPointCount returns zero. When this value is returned, use the default value for the feature type as explained below:

· The default value for the 'point feature type' is 1.
· The default value for the 'for line feature type' is 2.
· The default value for the 'for polygon feature type' is 4 (see note below).

For polygons, the default value of 4 may cause confusion because MOLE expects all polygons to be closed polygons (for example, that IPolygonClose() is called on the geometry). This implies that all of these closed polygons have a minimum of 4 points, where the endpoint is at the start point.

For example, for a support by fire position graphic, G*GPOAS*******X, the standard specifies four anchor points, but MOLE requires five points; the fifth point closes the polygon and is positioned on the start point.

The following example (as pseudo code) shows how one might implement this substitution (for zero):

IGeometryLimits geoLimits = graphicDef as IGeometryLimits;
int minNumberOfPoints = geoLimits.MinPointCount;
int maxNumberOfPoints = geoLimits.MaxPointCount;
int nGeoType = geoLimits.GeometryType;

if (nGeoType == 1) // Point
// min/maxNumberOfPoints do not need to be checked for points
minNumberOfPoints = 1;
maxNumberOfPoints = 1;
else if (nGeoType == 3) // Line
if (minNumberOfPoints == 0)
minNumberOfPoints = 2;

if (maxNumberOfPoints == 0)
maxNumberOfPoints = INFINITY_TAG; // Tag for no bound
else if (nGeoType == 4) // Polygon/Area
if (minNumberOfPoints == 0)
minNumberOfPoints = 4; // Minimum of 4 points in a *closed* polygon

if (maxNumberOfPoints == 0)
maxNumberOfPoints = INFINITY_TAG; // Tag for no bound

Article ID:000010327

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