Altitude Deviation (Batch QC Tab Parameters)

Use the Altitude Deviation tab (QCHEIGHT GX) to carry out quality control on survey flying height.

Altitude Deviation tab options

Radar-altimeter channel	Select the Radar-altimeter channel to check for altitude deviation. This is a required field. Script Parameter: QCHEIGHT.CHAN
Topography channel	Select the Topography channel for checking absolute altitude deviation. This is a required field. Script Parameter: QCHEIGHT.TOPO
Nominal flight height	Specify the Nominal flight height. This is a required field. Script Parameter: QCHEIGHT.NOMINAL
Minimum flight height	If specified, this is an absolute minimum height. All points below this height relative to the topography are flagged. Script Parameter: QCHEIGHT.MINHEIGHT
Maximum flight height	If specified, this is an absolute maximum height. All points above this height relative to the topography are flagged. Script Parameter: QCHEIGHT.MINHEIGHT
Maximum deviation	Specify the maximum deviation at each reading location. Script Parameter: QCHEIGHT.MAXDEV
Allowed deviation	Specify the allowed deviation from the nominal height. Script Parameter: QCHEIGHT.ALLDEV
Over a distance of	Specify the "over a distance of" parameter such that, if the Allowed deviation value (see above) is exceeded for this specified distance then the line will be flagged as out of survey specification. Script Parameter: QCHEIGHT.DIST

Application Notes

This GX assumes that the current database is the one containing the actual survey data. The database is called the survey database. If you wish to process a different database, you may browse to add it to the project or select one from the workspace list.

Quality Control Specifications and Indicators

This tab permits three separate specifications to be tested to determine whether the airplane flight heights are within specification or not.

At each reading location, the flight height must be less than the nominal flight height plus the maximum deviation and more than the nominal flight height minus the maximum deviation.
The flight height must be less than the nominal height plus the allowed deviation or more than the nominal height minus the allowed deviation for a distance less than the specified distance.
If the corresponding parameters are specified, the flight height must be above the minimum flying height and below a maximum elevation at all times.

You can apply any combination of these tests. The check against the absolute flying height range takes precedence over test 1 and 2.

To disable a test leave the text box blank.

This tab creates a flag channel, called Flag_Height, which contains numbers from -4 to 4 inclusive to indicate the result of the quality control test on flight line height.

Indicators Definition

Flag	Description
0	Flight height passes both tests
±1	Flight height fails the 1st (Maximum deviation) test
±2	Flight height fails the 2nd test
±3	Flight height fails both tests
±4	Flight height is above maximum(+) / below minimum (-) elevation

Positive values in the flag channel indicate that the actual flight height is higher than the nominal and negative values indicate that the actual flight height is less than the nominal height.

Calculation of Distances

When the 2nd specification is tested, the cumulative distance along the actual survey path is used instead of the distance along the ideal line path.

All failures are indicated with a single colour on the map. If you would like to illustrate the type of failure on the map, generate a symbol plot of the Flag_Height channel using any one of the symbol options (Colour Range Symbols, Proportional Size, and Colour Range).