I'm using Power Geopak SS4 .878. 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.
My existing DTM from survey is in one file. In my corridor file for phase 6, I have complex terrain model that serves to simulate the existing terrain at the beginning of phase 6. (This seems to affect other phases too, but at the moment I'm working in phase 6.) As mentioned, both files use survey feet.
I took a look at corresponding points out on the fringe. I measured the distance, which turned out to be exactly the value of the lower (southwesterly) coordinate*[(1-2e-6)^-1 - 1]. The factor here suggests that one file must be survey and the other international. But when I attached the files, no warning showed up. In the references list, I noticed that the DTM file scale is 1:1 whether True Scale is on or off. (Otherwise, when the units differ, it flipflops between 1:1 and 1:1.000 002, or between 1:1 and 1.000 002:1.)
To clarify, the survey DTM holds the larger coordinates. Something in the system (apparently) is telling the complex terrain that the survey DTM's points are in international feet. Therefore, the complex terrain model uses smaller values for coordinates.
Apparent root of the problem:
In my phase 6 corridor file, where I also have created the complex terrain model, my survey DTM is attached with 1:1 scaling. The complex terrain model is scaled down as mentioned, so looking at a fringe point, I see two distinct points: one from the survey, one from the slightly smaller scale. I have no explanation for this behavior.
Further exploration:
I took the time to get into VBA to confirm the units. In both the survey DTM file and the corridor file,
MasterUnit.UnitsPerBaseNumerator = 39370 MasterUnit.UnitsPerBaseDenominator = 12000
to represent 39.37 inches per meter over 12 inches per foot. Same for StorageUnit.
SubUnit.UnitsPerBaseNumerator = 39370 Subunit.UnitsPerBaseDenominator = 1200
to represent 39.37 inches per meter over 1.2 inches per tenth of a foot.
Any ideas on what might be the problem here? Any ideas on how to fix this?
When you say "Survey DTM", is this a native surface that is stored in a DTM file? Or is it a terrain model? If it is a native DTM, you will need to convert the data using Surface>Edit Surface>Transform Surface.
By survey DTM, I mean an OpenRoads terrain element which represents survey points. It was created either by importing from a CSV points file directly as OpenRoads points, or from COGO points that had been visualized. (I don't recall which route I took.) Regarding Surface>Edit Surface>Transform Surface, that is a path I'm unfamiliar with. Is there a key-in for that (if it is still a valid step), or some other way to get to that tool? Also, unless the transform surface tool allows scaling, that isn't the appropriate move. Unscaled translation is definitely not what I want to do. What's strange here is that I'm using the existing survey DTM as the base, at whatever given coordinates, and what comes out in my complex terrain is that the coordinates are scaled down as if they were for international feet, when on the contrary they were for survey feet, and they're in a survey feet file.
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.