Manual point measurement
Measuring Ground Control Points
Ground Control point measurement is not mandatory in HxMap, but it is recommended to refine the accuracy of the exterior orientation or to detect and remove possible datum differences. Ground control measurement can be performed after APM only.
Once ground control point coordinates are imported into a HxMap Triangulation project, they are visible in the MapView as blue squares (check points: blue triangles) and appear in the Points tab. You can open the points tab from the “View” menu in case it is not yet visible.
In order to measure a single point, select the point in the Points tab and perform a right mouse-click. Select "Measure" to open the Measurement window.
Alternatively, move the cursor to a GCP position in the MapView and press ALT+ right Mouseclick. A pocket menu allows to select option "Measure ground point". If selected, the mMeasurement window will populate and open the images containing the selected point. Also, that point becomes highlighted within the Point tab.
The Measurement Window
Before you start measuring, make sure you pick a product template representing the same band you used for point matching. It is furthermore recommended to have the Auto-stretch option enabled.
The proposed point position appears in the center of each view.
display is adjusted to be “north-up” for all images
Existing measurements are marked by a pink circle.
In order to place a measurement, move the cursor into a measurements window and press ALT.
The cursor will change into a measurement cross. Perform a left mouse-click to place the point.
Once the measurement is placed, you can transfer it to other images. To do so, perform a right mouseclick to launch the pocket menu and select option "Auto-correlate using this image"
To delete a particular measurement, move the cursor into the measurement window, perform a right mouseclick to launch the pocket menu and select option Remove image point from this image"
Adding New Tie Points
In areas with poor structure such as forest, APM may not have generated enough good-quality points to guarantee a solid block geometry. In such cases it may become necessary to manually add and measure tie points.
Use the map view to detect areas with no points or only few tie point measurements and move the cursor to that location. Perform a ALT+ right mouseclick to open the pocket menu and select option "Create tie point".
This causes a point to be placed at the selected location in the MapView. This point will also be added to the Point Tab. Per default the first point you place that way gets ID 1. The ID for additional points increment by 1.
With the new point available in the MapView, use one of the procedures described in the previous section to add measurements to that point.