Hi Everybody:
I have two personal geodatabases (.MDB file). Both GDB have a polyline feature class (Polyline ZM) and a point feature class (Point ZM). I did the following steps on each GDBs individually:
1. open and display the point feature class and polyline feature class together in ArcMap. No other feature classes are added to ArcMap.
2. start ArcMap edit session, turn on only vertex snapping in snapping toolbar.
3. choose the point feature template in the "Create Features" window and the "Point" construction tool.
4. Snap onto a line in the polyline feature layer and click to create a new point feature.
5. In the attribute table of the point feature class, find a double type field or text type field, use "Calculate Geometry" function on column header context menu to calculate the Z-Coordinate in unit of cm.
Then I observed different results from these two GDBs: GDB A always have the value zero for the Z-Coordinate of the newly created points; GDB B always gives a very tiny non-zero Z-coordinate (about 0.0001 cm).
Do you have idea why this difference can happen?
Finding the reason for this phenomenon can help me to resolve an issue in an ArcMap extension I developed. This extension found that the newly created points by snapping in GDB B are not exactly on the polylines, and keep giving warnings.
Following are more details:
i. The polyline features in both GDBs have Z-Coordinates between 300 ft and 700 ft. The Z-Coordinate generated in GDB B is consistently a tiny value (around 0.0001 cm) different from the vertex it snaps to.
ii. If I check the properties from ArcCatalog, both GDBs have the same spatial reference for their feature classes: "GCS_WGS_1984" for XY coordinate system and "WGS_1984" for Z Coordinate system.
iii. GDB A and GDB B contains features in different extents.
iv. I am using ArcGIS 10.0 SP4, build 4000.
Any idea?
I have two personal geodatabases (.MDB file). Both GDB have a polyline feature class (Polyline ZM) and a point feature class (Point ZM). I did the following steps on each GDBs individually:
1. open and display the point feature class and polyline feature class together in ArcMap. No other feature classes are added to ArcMap.
2. start ArcMap edit session, turn on only vertex snapping in snapping toolbar.
3. choose the point feature template in the "Create Features" window and the "Point" construction tool.
4. Snap onto a line in the polyline feature layer and click to create a new point feature.
5. In the attribute table of the point feature class, find a double type field or text type field, use "Calculate Geometry" function on column header context menu to calculate the Z-Coordinate in unit of cm.
Then I observed different results from these two GDBs: GDB A always have the value zero for the Z-Coordinate of the newly created points; GDB B always gives a very tiny non-zero Z-coordinate (about 0.0001 cm).
Do you have idea why this difference can happen?
Finding the reason for this phenomenon can help me to resolve an issue in an ArcMap extension I developed. This extension found that the newly created points by snapping in GDB B are not exactly on the polylines, and keep giving warnings.
Following are more details:
i. The polyline features in both GDBs have Z-Coordinates between 300 ft and 700 ft. The Z-Coordinate generated in GDB B is consistently a tiny value (around 0.0001 cm) different from the vertex it snaps to.
ii. If I check the properties from ArcCatalog, both GDBs have the same spatial reference for their feature classes: "GCS_WGS_1984" for XY coordinate system and "WGS_1984" for Z Coordinate system.
iii. GDB A and GDB B contains features in different extents.
iv. I am using ArcGIS 10.0 SP4, build 4000.
Any idea?