Process SAE Data
All the data is held in a .db file which can be opened with “Excel” and the selected table exported as a dos “.csv” file.
Use excel to Build the following files from their respective tables
As the coordinate data is held in geographic format (Latitude, longitude), an appropriate datum and zone should be set for the job.
The system first reads in the plan data and sets up the survey date, surveyor and lodged date.
The “tags” data is read next and analysed. . A typical feature tag would be 27DP23478 with the alphabetic characters being used to define the plan type and separate the lot number from the plan number. The lot number is split from the plan number and a new parcel created for each record. If a plan record does not exist it is created also
If a tag does not have “alptha separators” or if it only has a plan number a default lot name is used for the lot number.
The tag record has the lot extents and this is used to calculate the lot centroid.
The points file is then read in and a point created for each point in the file. As each point is read in its coordinates are converted to the current projection (eastings and northings). As each point is converted it is checked to see if it is reasonable for the projection.
All the lines are then read in and stored as lines in a dummy lot. The plan number from the lines record is held as an extra attribute to the line in this lot.
Lots are then built from the data as follows:
For each parcel, the line closest to the parcel which is also from the same plan as the parcel is used as a starting line. Lines are then added going in a clockwise direction until the “from point” of the starting line is reached. If the chain of lines runs out before the parcel closes, then the parcel is flagged as being “unclosed”. As each line is selected it is flagged as being “used”.
Typical errors are as follows:
After all the parcel have been built, the lines from the dummy lot are scanned again and any that have not been used are added to lots as “radiations” and the dummy parcel is then deleted.
Unused points. These could be associated with unused lines or may be simply points for which no data exists
- Failure to build lines around a parcel. This can be caused by various reasons. The lot will appear without any lines.
- Parcels with the same centroid. Sometimes all the parcels in a plan have the same centroid as the plan exxtents have been used instead of individual lot extents. All the lot numbers will be on top of each other and all the lots in the plan will be identical.
- Unused lines. These may be left over from the lot building process. They may refer to a non existing plan or may be isolated connections.