[OR] Survey foot-International foot scaling observed in complex terrain model where all models are in survey feet

Can no one explain this issue or suggest a workaround?

To review, perhaps providing better specificity:

1. I have a ground-survey points file using survey feet for the storage and working units. It holds an OpenRoads terrain model that comes, almost completely, from OpenRoads points. It may be worth noting that it had been converted from international feet, but VBA reports that it is indeed using survey feet. (From the beginning, the coordinates were always valid for survey feet; the storage and working units were simply incorrect from the beginning.)

2. I have an air-points file using survey feet for the storage and working units. It holds an OpenRoads terrain model which simulates the location of a power-line transmission tower. (This is by way of obvious example, since it's an obvious feature.)

3. In the ground-survey points file, I attach the air-points file. I create a composite terrain model with the air-points "terrain" being merged onto the ground-survey terrain. Everything coordinate in the composite terrain is scaled to 0.999 998 ft/ft (X, Y, and Z). So a given point at the coordinates 2125247.1514, 1020395.2372, 161.7734 in the unmodified survey terrain is now represented in the composite terrain at the coordinates 2125242.9009, 1020393.1964, 161.7731.

4. For another level of certainty, I deleted the composite terrain. I scaled the air-points file to be 0.999 998 ft/ft (according to the references list, 1:1.000 002, but I entered it as 0.999 998:1), so that now that file is located where the composite terrain places it. I create a new composite terrain model using the same approach as I did before. The new composite terrain model now places the transmission tower at the same location as the transmission tower within the air-points file (scaled as mentioned, at the same coordinates as was seen in the complex model created in observation 3 above).

So: What would cause this to happen, and how can it be fixed?

Edit: I guess the upshot is that the terrain model retains the coordinates that it always had, but it retains them in the original units, no matter the design file units.

The second sentence in my original post, and following, was this:

My project started with international feet as my working and storage units but with coordinates matching survey feet. I've converted all files to survey feet using a VBA macro. I know that you can expect to get a message when attaching a survey feet file to an international feet file and vice versa, warning you that the coordinates are going to be off. I haven't been getting that message.

In the end, a more local contact reminded me that once you have civil geometry in a file, you can't just convert units and assume all is well. Clearly this is true, at least in this case. Are there any plans to change this fact?

For the record, this is a set of steps to cause the problem:

1. Start with a non-survey foot seed.
2. Import survey points whose coordinates are in survey feet.
3. Construct a terrain model from points.
4. Change units to survey feet. At this point, the terrain doesn't represent anything real, but you wouldn't know this.
5. Compare the terrain's vertices with the points and breaks used to construct the terrain. They will match.
6. Create a corridor, and see from the cross sections that the tie-downs match the terrain.

To see the problem:

1. Create another terrain model.
2. Merge this new terrain model onto the one created earlier.
3. Compare the terrains' vertices and you'll see that one of them is scaled from the original units to survey feet.
4. Notice the difference as you view the corridor's cross sections.

To avoid the problem: Use the correct seed file from the beginning as you are creating your terrain model file. If you have a terrain model already provided, but not the source points, shucks. You'll need the original points.

To fix the problem, the best I can work out at the moment is this:

1. Delete the terrain model that had been created prior to the change of units. (You probably shouldn't do this unless you can retrace all the points and breaks.)
2. Set appropriate units for the coordinates given (in this case, survey feet).
3. This is theoretical, and I don't know whether the units are stored with the coordinates of the points if they had been placed as civil points.
4. Reconstruct the terrain model from points and breaks.

Strangely enough, I found that when I merge the old terrain onto a new one, there is no scaling done. Moving forward, if I merge any terrain model onto this one, there seems to be no issue.

Another inconsistency. Meanwhile, I'll use it.

The second sentence in my original post, and following, was this:

My project started with international feet as my working and storage units but with coordinates matching survey feet. I've converted all files to survey feet using a VBA macro. I know that you can expect to get a message when attaching a survey feet file to an international feet file and vice versa, warning you that the coordinates are going to be off. I haven't been getting that message.

In the end, a more local contact reminded me that once you have civil geometry in a file, you can't just convert units and assume all is well. Clearly this is true, at least in this case. Are there any plans to change this fact?

For the record, this is a set of steps to cause the problem:

1. Start with a non-survey foot seed.
2. Import survey points whose coordinates are in survey feet.
3. Construct a terrain model from points.
4. Change units to survey feet. At this point, the terrain doesn't represent anything real, but you wouldn't know this.
5. Compare the terrain's vertices with the points and breaks used to construct the terrain. They will match.
6. Create a corridor, and see from the cross sections that the tie-downs match the terrain.

To see the problem:

1. Create another terrain model.
2. Merge this new terrain model onto the one created earlier.
3. Compare the terrains' vertices and you'll see that one of them is scaled from the original units to survey feet.
4. Notice the difference as you view the corridor's cross sections.

To avoid the problem: Use the correct seed file from the beginning as you are creating your terrain model file. If you have a terrain model already provided, but not the source points, shucks. You'll need the original points.

To fix the problem, the best I can work out at the moment is this:

1. Delete the terrain model that had been created prior to the change of units. (You probably shouldn't do this unless you can retrace all the points and breaks.)
2. Set appropriate units for the coordinates given (in this case, survey feet).
3. This is theoretical, and I don't know whether the units are stored with the coordinates of the points if they had been placed as civil points.
4. Reconstruct the terrain model from points and breaks.

Strangely enough, I found that when I merge the old terrain onto a new one, there is no scaling done. Moving forward, if I merge any terrain model onto this one, there seems to be no issue.

Another inconsistency. Meanwhile, I'll use it.