Table 4 Definition of FOM values
From: Digital elevation model and orthophotographs of Greenland based on aerial photographs from 1978–1987
FOM VALUE | FOM TITLE | DEFINITION |
|---|---|---|
0 | SMALLEST_FOM | Lowest numerical value for a FOM (set to 0). |
1 | OUTSIDE_BOUNDARY | Outside the extraction boundary defined as a polygon when the grid was created or defined as a rectangle. The OUTSIDE_BOUNDARY posts are not processed by any SOCET SET applications. |
2 | START_SUSPECT_FOM | FOMs between this value and the START_GOOD_FOMS were flagged by the correlation process and have interpolated elevations from the surrounding ‘good’ FOM points. Points with FOMs in this range (START_SUSPECT_FOM to START_GOOD_FOMS) may have good elevations since they were interpolated from the surrounding elevation data. |
3 | INSIDE_BOUNDARY | After the DTM is created, all FOMs will have either an INSIDE_BOUNDARY FOM or an OUTSIDE_BOUNDARY FOM. The INSIDE_BOUNDARY FOMs are assigned to points before they have gone through the correlation process or interactive edit process. |
4 | EXTRAPOLATED | Points which are on the edge of the DTM grid and have assigned elevations from points with good FOMs internal to the grid. |
5 | INTER_OPER_ BAD | INTEREST OPERATOR BAD indicates a point failed the initial correlation process and a subsequent interest operator correlation process. |
6 | HIGH_SLOPE | The elevation assigned to the point after correlation failed an elevation slope threshold check and has been subsequently interpolated from surrounding data. |
7 | TEMPORARY_FLAG | Used by software. |
8 | SPIKE_POST | The elevation assigned to the point after correlation failed an elevation spike or well threshold check. The spike or well was determined from the surrounding elevation data. The elevation for the point has been interpolated after it was identified as a spike or well. |
9 | LOW_CORRELATION_ CURVATURE | The elevation assigned to the point after correlation failed an elevation spike or well threshold check. The spike or well was determined from the surrounding elevation data. The elevation for the point has been interpolated after it was identified as a spike or well. |
10 | LARGE_DIFF_SIGNAL_ POWER | The signal power difference between the right and left image patches used by the correlator was lower than the threshold. The elevation for the point has been interpolated after it was identified as having a large difference in signal power. |
11 | EXCESSIVE_SHIFT | The maximum correlation was found on the first or last sample in the correlation image buffer. The elevation for the point has been interpolated after it was identified as having a secondary peak. |
12 | EDGE_OF_IMAGE | The image patch for correlation was too close to the edge of the image and could not be used by the correlator. The elevation for the point has been interpolated or extrapolated after it was identified as being on the edge of the image. |
13 | LOW_SIGNAL_POWER | The signal power computed for the right or left image patch in the correlator did not meet the signal power cutoff threshold. The elevation for the point has been interpolated after it was identified as having a low signal power. |
14 | LARGE_ELEV_CHANGE | The change in elevation during iterations within the correlator exceeds a threshold. |
15 | LOW_CORRELATION | The correlation coefficient computed for the point was below the threshold. The elevation for the point has been interpolated after it was identified as having a low correlation. |
17 | INVISIBLE | The post/point is not used to generate terrain graphics. |
18 | SECONDARY_ CORRELATION_PEAK | There was a secondary correlation peak identified by the correlator. The secondary peak may be almost as large as the primary correlation peak. Therefore, the point is considered as suspect. The elevation for the point has been interpolated after it was identified as having a secondary peak. |
19 | EXCESSIVE_V_SHIFT | The maximum correlation was found on the first or last line in the correlation image buffer. The elevation for the point has been interpolated after it was identified as having a secondary peak. |
20 | ELEVATED_POST | The post is identified as a none bare earth post such as on top of a tree or building. Its elevation may have been lowered to the ground by a bare earth tool. |
21 | START_GOOD_FOMS | Points with FOMs greater than START_GOOD_FOMS are considered good. See START_SUSPECT_FOMS for more information. |
22 | MANUALLY_MEASURED | The point has been edited using the Interactive Terrain Edit tools post editor or profile editor. |
23–26 | LAKE_FILLED, PLANE_FILLED, SMOOTHED, DWI | The point has been edited using one of the Interactive Terrain Edit area tools. Does not occur in this data set. |
27 | THINNED | The point has been marked as redundant by the Interactive Terrain Edit area edit tool so that it can be thinned by the DTM Export function. |
28 | IMPORTED_DTED | The point has been imported from DTED. Does not occur in this data set. |
29 | GEOMORPHIC | The point has been edited using one of the Interactive Terrain Edit geomorphic tools. Does not occur in this data set. |
30 | INTERPOLATED | The point has been edited using an ITE tool for clipping an area, or the point has been imported from a DTM created outside the workstation. Does not occur in this data set. |
31 | SEED_POINT | The point is from a see point such as a control point, or a tie point etc. |
32 | EDGE_POINT | This post/point is matched by edge matching. |
33 | CORNER_POINT | This is a corner post identified by one of the bare earth tools. |
34–38 | ONERETURNS, | LIDAR point/post from the first-fifth return. Does not occur in this data set. |
TWORETURNS, | ||
THREERETURNS, | ||
FOURRETURNS, | ||
FIVERETURNS | ||
39 | LARGEST_FOM | The largest possible numerical FOM value for a post which did not automatically correlate. |
40–99 | FOMs in this range indicate that the post successfully correlated. FOMs are proportional to the correlation coefficient, so the larger the number, the better the quality of the measurement. |
