Home - General / All posts - Traverse with sequential curves
 dchall81,012 post(s) #10-Nov-23 00:49 I'm wondering if there's a better way to do the sequential curves for a CAD drawing of a neighborhood? Here is the original drawing showing how a typical neighborhood is/was drawn in the 1950s.I decided to disregard the original directional calls after using them. Not all the angles are on the drawing, so instead I imported the image of the CAD drawing and measured the angles for use in the traverse data. Lets look at the lots on the south side of Laramie Drive. Beginning at the nw corner of those lots there is no angle for the direction of the lots. I tried using the angles highlighted in yellow, but when you measure the angles, they are all different and fall in between the 75° angle on the bottom and the 85° angle at the top of the drawing. So I measured the angle and used 83°. For the curves I converted the Delta angle shown in the curve data to decimal degrees and took the fractional amount of arc distance (Length in the Curve Data Table) to determine the actual Delta for each segment of the curve. Here is the data as input to the traverse.DT QBDU DMSSP 2145748.572722472 13733383.797666853DD N83-49-22.8E 86.35DD N83-49-22.8E 90DD N83-49-22.8E 90DD N83-49-22.8E 87.73TC D 0-10-15.29 A 2.27 RTC D 6-46-34.68 A 90 RTC D 6-46-34.68 A 90 RTC D 6-3-10.02 A 80.39 RDD S75-56-24E 9.61DD S75-56-24E 90DD S75-56-24E 85TC D 90-00-00 A 23.56 RDD S13-27-25.2W 110.99TC D 1-14-11.08 A 14.01 RDD N75-56-24W 99.85DD N75-56-24W 90DD N75-56-24W 9.61TC D 6-10-52.96 A 65.6 LTC D 6-55-13.64 A 73.44 LTC D 6-55-13.64 A 73.44 LTC D 3-56-33.72 A 41.84 LDD S80-38-49.2W 47.88DD S80-38-49.2W 90.19DD S80-38-49.2W 90.19DD S80-38-49.2W 82.7DD N13-29-16.8W 145.58TC D 97-22-39 A 25.49 RSo for the first fragment of curve moving east on Laramie, the text is TC D 0-10-15.29 A 2.27 R, showing a very small segment for Delta across 2.27 feet of arc.  Then for the subsequent parts of the curve I did the same thing.  The idea mostly worked if you don't mind being 3 feet off from closing the line on a very small segment of area.  I can't help think there's a more elegant way to do this. Attachments: Northwood Plat Annotated.jpg
 dchall81,012 post(s) #10-Nov-23 01:08 Wow! The formatting on that post came out awful. I'm going to try it without so many bells and whistles. Also I attached an mxb file. Here's the redo without any formatting. I'm wondering if there's a better way to do the sequential curves for a CAD drawing of a neighborhood? Here is the original drawing showing how a typical neighborhood is/was drawn in the 1950s.I decided to disregard the original directional calls after using them. Not all the angles are on the drawing, so instead I imported the image of the CAD drawing and measured the angles for use in the traverse data. Lets look at the lots on the south side of Laramie Drive. Beginning at the nw corner of those lots there is no angle for the direction of the lots. I tried using the angles highlighted in yellow, but when you measure the angles, they are all different and fall in between the 75° angle on the bottom and the 85° angle at the top of the drawing. So I measured the angle and used 83°. For the curves I converted the Delta angle shown in the curve data to decimal degrees and took the fractional amount of arc distance (Length in the Curve Data Table) to determine the actual Delta for each segment of the curve. Here is the data as input to the traverse.DT QBDU DMSSP 2145748.572722472 13733383.797666853DD N83-49-22.8E 86.35DD N83-49-22.8E 90DD N83-49-22.8E 90DD N83-49-22.8E 87.73TC D 0-10-15.29 A 2.27 RTC D 6-46-34.68 A 90 RTC D 6-46-34.68 A 90 RTC D 6-3-10.02 A 80.39 RDD S75-56-24E 9.61DD S75-56-24E 90DD S75-56-24E 85TC D 90-00-00 A 23.56 RDD S13-27-25.2W 110.99TC D 1-14-11.08 A 14.01 RDD N75-56-24W 99.85DD N75-56-24W 90DD N75-56-24W 9.61TC D 6-10-52.96 A 65.6 LTC D 6-55-13.64 A 73.44 LTC D 6-55-13.64 A 73.44 LTC D 3-56-33.72 A 41.84 LDD S80-38-49.2W 47.88DD S80-38-49.2W 90.19DD S80-38-49.2W 90.19DD S80-38-49.2W 82.7DD N13-29-16.8W 145.58TC D 97-22-39 A 25.49 RSo for the first fragment of curve moving east on Laramie, the text is TC D 0-10-15.29 A 2.27 R, showing a very small segment for Delta across 2.27 feet of arc. Then for the subsequent parts of the curve I did the same thing. The idea mostly worked if you don't mind being 3 feet off from closing the line on a very small segment of area. I can't help think there's a more elegant way to do this. Attachments: Metes and Bounds Laramie Block.mxb
 Mike Pelletier2,138 post(s) #20-Nov-23 19:09 Appreciate the challenge you have. I like to first think about the potential sources of error and how accurate I need to be. Getting accurate GPS readings for survey pins would sure help. I think the survey and it's drawing (plat) is accurate. However, it appears the scan is quite distorted. The Google image should be pretty distortion free but maybe not super good X,Y. Some fences, alleys, and buildings can show property lines but no guarantees. There's also the rotation and scaling error associated with the coordinate system. That surely affects the angle and maybe the scaling a tad. There are ways to determine the amount of those.Manifold is great with trying different registrations of the plat, so you can try different clues in the Google image as to where property lines lie. Generally, I first try to register the plat with 2 control points to avoid warping the image, but in your case it is already warped so you need to use more. Attached is my attempt. I drew to lines where the plat has long straight dimensions and then used those for control points. That should get the scale close. Once happy with the rotation and shift, I'd register it and then trace the property lines because I don't need to be any more accurate than that.When registering an image it would be nice if Manifold had a way to lock an image scale to dimensions shown on the plat, while making it easy to rotate and shift the image with just 2 points to avoid warping the image.Attachments: Metes and Bounds Laramie Block modified.mxb
 dchall81,012 post(s) #21-Nov-23 05:16 Thanks Mike. I was hoping you'd see this question. I haven't gotten to the registration part of the problem yet. The hang up is how slow it is parsing the curves. For example curve 50 covers 19-46-35 degrees over four lots (N.C.B 11820, lots 4-7). The arc needs to be divided into pieces according to the arc distance as shown on the drawing. The traverse for the arc on curve 50 looks like this.(lot 4) TC D 0-10-15.29 A 2.27 R(lot 5) TC D 6-46-34.68 A 90 R(lot 6) TC D 6-46-34.68 A 90 R(lot 7) TC D 6-3-10.02 A 80.39 RThe arc fragmentation process is not that difficult, but it is fiddly. I was hoping there would be an elegant way to do it inside of Manifold or with special coding within the traverse instructions. Are you suggesting it is easier to get the drawing registered and then draw lines from corner to corner along the registered drawing? I mean, that is easy, but it doesn't capture the curves.
 Mike Pelletier2,138 post(s) #21-Nov-23 16:59 Sorry, I can't think of an easy way to break down the curves. For what I do, yes it is easier to digitize parcels off a georegistered plat than it is to COGO the parcels and then scale, shift, and rotate them to fit in the coordinate system, which destroys the dimensions and angles. My approach is to keep the surveyed plat image available to users for dimensions rather than have my parcel lines be used for that. Curves don't survive many of the Manifold operations like topology, split, etc. Curves are pretty but not needed for what I do. However, it is nice to be able to draw a line between the ends of a curve, then convert it to a circle, adjust it to match the curve, and then use the split command to chop up the curve where parcel lines intersect.Hope that helps.
 dchall81,012 post(s) #21-Nov-23 21:04 Interesting approach. I'll try that after Thanksgiving.