RiverCAD Difficulties with Resizing and Rescaling

Chris Maeder,

As per our conversation this morning (May 4, 1998), I have attached a copy of one of our files. The zipped file is approximately 1.8 MB. I will send a copy of the original file (not shifted or rescaled) in a second email.

Summary of Problem:

Our RiverCAD files were created from original CAD files in Microstation format. The coordinate system for some of the files was shifted and rescaled due to a problem in Microstation. Unfortunately, we did not catch the problem until we had already completed much of our RiverCAD work. We would now like to resize and rescale the drawings to match our other CAD and GIS data. We need to attach additional contour data to the file to extend our models. We will either have to correct the problem in the original files, or shift the additional data to match the original files. Our eventual goal is to have the data in a single, consistant coordinate system.

Coordinate System:
1. The original coordinate system for the data was State Plane, Texas South Central Zone.
2. The incorrect coordinate system is based on Microstation positional units.
a. These coordinates are shifted from positive coordinates on the order of x=2,000,000 and y=13,000,000 to x=-18,000 and y=-200,000.
b. The drawing is also rescaled by a factor of 1/100 (contour that should read z=100 reads z=1).

My Steps:
1. Used the RiverCAD scale tool to increase the scale by a factor of 100 (with a base coordinate of 0,0,0).
2. Used the RiverCAD move tool to shift the drawing coordinates to the appropriate location.
3. Reset the 2D/3D horizontal and vertical scales from 100 to 1 (file/configure/topomap dialog)
4. Steps 1 and 2 were performed on the drawing portion of the file only. The cross section grids were not moved or resized. I did use the file/configure/section grids tool to move them later.

Problem:
1. The INQUIRE tool returns the proper elevation for the contours in the drawing, however, new cross sections are not created correctly.
2. If a new section is cut, the horizontal scale will be accurate while the vertical scale will still be off by a factor of 100.
3. If I reset the vertical scale factor (file/configure/section grids) to 100, the cross section will be correct.
4. In either case, editing handles will not appear on the new cross section in the topo map view (for picking overbank points, etc.)

Other Observations:
1. I tried running the model and plotting the floodplain on the topo map. The floodplain appeared to plot correctly.
2. The model also correctly restricted the floodplain limits by the cross sections.

Some unrelated RiverCAD issues:
1. Why is the screen layout (locations of windows) not saved with the file. Each time I open the file, I have to rearrange the window layout.
2. Does the drawing have to regenrate any time another window, tool bar, or dialog box moves accross the drawing window. This can slow things down considerably in a large file.
3. The undo command does not seem to work in any of the modules.

Thank you for your help on these issues. Thank you also for clearing up my question about zooming in and out in Autopan.

Karl McArhtur, E.I.T.
Engineering Staff
Water Resources
Espey, Huston &Associates, Inc.
Wk ph: (512) 329-8342 ext. 9587
Email: kmcarthur@eha.com

Dear Mr McArthur,

We looked into the drawing file you sent us. Basically it's recommended that you unload RiverCAD before modifying the drawing using any CAD command. This can be done by "(unload "rcad.dll") command.

1. The main problem is caused by that the SCALE command of the CAD engine does scale the elevation of each vertex on the 2D polylines. But for a 2D polyline there is a dummy point at the header and the dummy point is supposed to contain the elevation of all the vertex. The CAD engine does not SCALE this value. Our INQUIRE command checks the vertex but when you cut cross-section, the value from the header is used. This is a bug in the CAD engine and I will let the developers know about this. Currently I think you have to use the Elevation scale in the Topo Map Configure dialog.

2. RiverCAD does draw the new cross-section labels after you scale the drawing. But just it still uses the orginal font size (which can be set in the same dialog where you set the Topo Map scale). You can increase the font size by 100 times and you should be able to see the labels.

3. The floodplain mapping module uses the values from the elevation from the vertex too so the results are correct.

4. Currently the CAD engine does not remember the viewport layout. I will let the developers know and see if they can implement this feature.

5. RiverCAD regen the drawing when you issue the first RiverCAD command. It should not regen after this unless you open a new drawing file.

6. The undo command is disabled while RiverCAD is loaded. This is because we do not have control of what the last command was. If RiverCAD entities is modified by non-RiverCAD command, it will damage our database.

Please contact me if you have any questions.

Regards,

Chung-ping Liang
BOSS International