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Plotting Property Boundaries - Feature Requests


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#1 Tim Osborn

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Posted 19 April 2006 - 09:33 PM

I know of several professionals who are using ExpertGPS to assist in surveying and property management, so this would be a good discussion to start in the GIS, CAD, and other professional use forum.

If you have a property description and can identify the coordinates of the starting point, send me an email with the details, and I'll work on a way to let you turn the legal description into a route or shape in ExpertGPS.


Thanks Dan! I've attached a table that contains a fairly simple real-world property description. It's useful because when overlaid on a DOQ (aerial) map, you can readily see if the property lines plotted in ExpertGPS line up with obvious physical features. The property is located in Section 8, Township 15N, Range 29W, 5th Principal Meridian (4 miles West of Elkins, Arkansas).

Posted Image

The starting point, which is not on the property boundary, is a quarter-section corner point in the Public Land Survey System (PLSS). So, how are we going to find that? I displayed a topo map of the Section in ExpertGPS, placed waypoints at the corners of the Section, connected them with a route, and then switched to Quick Map view. Since the NE Corner of the NW Quarter of Section 8 is .5 miles from the NE corner of the section, I made the waypoint at the NE corner a proximity waypoint with a radius of .5 miles. Where the proximity boundary and the northern boundary of the Section intersect is our starting point (35.99560, -94.07985, WGS-84), and I placed a waypoint there when zoomed way in (thus the need to do this in Quick Map view since the proximity boundary disappears in Topo map view). You could use the same basic approach to find other Quarter and Quarter-Quarter corner points by working from South-to North and East-to-West in a Section.

Posted Image

From there I used the Project Waypoint feature (with move to waypoint and add to route both checked) to enter the subsequent bearings and distances. Because ExpertGPS currently does not accept bearings in Quadrant format (N34:24:06W), which most property descriptions use, I converted the Quadrant bearings to Azimuth's in a spreadsheet I built. I really like the fact that the previous bearing and distance are persistent in the Project Waypoint window. It helps you to identify which bearing and distance you need to enter next in an often long list of such vectors. The Azimuth's associated with each Quadrant bearing are shown in the following table.

Posted Image


After inputting all of the bearings and distances, the property description closes within a couple of feet. But, switching to Aerial Photo Map view shows that the plotted boundaries don't quite line up with the actual property. Much of the eastern boundary is susposed to be running down the center of the County Road. The western boundary doesn't line up with the edge of the forest. This kind of small error is almost inevitable with most of the property descriptions I've plotted. ExpertGPS allows us to move the waypoints and route associated with the property, but doesn't currently allow us to rotate routes, tracks, or shapes and the associated waypoints. This plotted property boundary need to be moved West a little, and rotated a bit (about 1.7 degrees clockwise).

Posted Image


So, here are some of my requested enhancements/changes to make plotting property boundaries in ExpertGPS easier:

1) Allow input and display of Quadrant bearings (e.g N48:36:15W). It could be a new user selectable Bearing "Units of Measure" under Preferences.

2) Allow rotation of Routes, Tracks, Shapes, and their associated waypoints.

3) Add Chains and Rods to Distance Units of Measure (Preferences and Project Waypoint).

4) Allow user to specify the unit of measure for Area (Preferences). What defaults to Acres currently I might want to see in Square Feet or Hectares and visa versa.

5) Permit more precision to be displayed in the list view for Area, Distances, and Bearings. Currently, Bearings are shown only to the nearest degree, although "Project Waypoint" seems to accept hundredths of a degree or more.

6) Holding down the space bar and the mouse button temporarily invokes the hand (panning) map tool. When the space bar is released, the previously selected map tool is restored.

Thanks Dan

Tim Osborn

#2 Dan Foster

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Posted 20 April 2006 - 04:50 PM

Hold down the Ctrl key to quickly switch from the Route tool to the Move Map tool. Release to go back.

Secondary Actions for Map Tools

#3 Tim Osborn

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Posted 20 April 2006 - 06:21 PM

Dan:

That's good to know. I wasn't aware of the Secondary Actions for the map tools.

For me, panning around the map with the hand tool is almost a constant activity regardless of the Map Tool I have in use. You've already got several convenient ways to zoom the map (mouse scroll wheel, ctl+ or page-up to zoom in, ctl- or page-down to zoom out) that don't depend on the currently selected map tool , but you are missing the standard shortcut for panning....holding down the spacebar while click-dragging the mouse. I really hope that you will consider adding that shortcut.

Thanks

Tim Osborn

#4 Dan Foster

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Posted 21 April 2006 - 07:24 AM

Can you point me to some other mapping programs that use this standard shortcut?

The Ctrl-key behavior is used in Adobe Photoshop.
Hey, look at that! The Shift-key behavior is in Photoshop, as well!

#5 Tim Osborn

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Posted 21 April 2006 - 11:36 AM

I'm glad you mentioned Photoshop. I use Adobe Photoshop, Illustrator, and Acrobat alot, and all use the spacebar as a way of shifting to the hand panning tool regardless of what other tool you have selected at the time. I imagine Adobe InDesign uses the spacebar like this but I don't use that program. Some other programs I use (Punto Embroidery digitizing software, Macromedia Freehand) also try to be compatible with Illustrator and act this way. Most of the other mapping programs I have looked at like (OziExplorer, DLG Viewer, etc) have pretty clunky tools for moving and zooming, so I don't think they serve as particularly good models.

The main "viewing" shortcuts I use in Adobe applications are:

Ctl+ + to zoom in (ExpertGPS already has this)
Ctl+ - to zoom out (ExpertGPS already has this)
Ctl+ 0 to fit everything on the screen (Currently missing in ExpertGPS but like hitting * to Zoom to Show all Data)
Spacebar to switch cursor to hand tool (Currently missing in ExpertGPS)

You currently have the mouse scroll wheel set to vary the scale view of the map when the user scrolls the wheel. You might consider having panning (move map) invoked as long as the user holds down the scroll wheel (as a button) and moves the mouse. This would make it super easy to move around a map. That's the way it works in Terrain (mapping/GIS software by Softree).

Also, sort of in the same vein, we once talked about "Bookmarks" or "Named Views", where the user could cause the program save the current view (coordinates of point in center of screen, current map scale, perhaps type of map like aerial or topo or scanned) with a user-assigned name or shortcut so that it would be easy to go back to that exact view at any time. Adobe Illustrator has this feature as do most CAD programs.

Thanks for continually improving ExpertGPS!

Tim

#6 Dan Foster

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Posted 21 April 2006 - 11:53 AM

Thanks Dan! I've attached a table that contains a fairly simple real-world property description. It's useful because when overlaid on a DOQ (aerial) map, you can readily see if the property lines plotted in ExpertGPS line up with obvious physical features. The property is located in Section 8, Township 15N, Range 29W, 5th Principal Meridian (4 miles West of Elkins, Arkansas).


Tim,

Can you post (or email me) a copy of the spreadsheet you're using?

#7 Tim Osborn

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Posted 21 April 2006 - 12:36 PM

Dan:

I've emailed you the spreadsheet to your support2006 email address.

Thanks

Tim

#8 Dan Foster

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Posted 21 April 2006 - 04:34 PM

After inputting all of the bearings and distances, the property description closes within a couple of feet. But, switching to Aerial Photo Map view shows that the plotted boundaries don't quite line up with the actual property. This plotted property boundary need to be moved West a little, and rotated a bit (about 1.7 degrees clockwise).


I spent a good part of the day trying to understand why the rotation was needed, and why, in general, Public Land Survey System boundaries don't follow perfect 0, 90, 180, 270 degree bearings. Arkansas's PLSS is centered on this point, marking the Louisiana Purchase:

Fifth Principal Meridian(South Detail)
Adopted 1815. Governing surveys - Arkansas, Iowa, Minnesota, Missouri, North Dakota, and South Dakota. Initial Point - Latitude 34-38-45, Longitude 91-03-07

I looked at the PLSS lines on the topo map at that point, and even there where they started, the lines are about 1.0 to 1.5 degrees off a true bearing, as calculated in ExpertGPS. I suspect that this is a result of newer Earth models (datums and ellipsoids) since 1815.

The first line of your property description should be running along the PLSS section line. I checked the angle along the line as ExpertGPS calculates it, and compared it to the property description, and got a difference of 1.11 degrees. I added that offset to all of your azimuths, and got a solution similar to what you came up with. It still needed to be shifted West to run down the road centerline.


Here are some of the observations I had while working on this:
- I was worried I was going to mis-type a bearing and distance along the way and have to start over. It would be nice to be able to enter everything into Excel or a similar data grid, and then paste it into ExpertGPS.
- I'm trying to envision a "Rotate Selected Data" tool in ExpertGPS. What else could it be used for? Are there other reasons to have it, outside of this kind of property description?
- I can think of a few areas where the ability to import a list of azimuths and distances would be useful:
- property descriptions
- setting up regularly-spaced sampling grids for a scientific survey
- creating geometric shapes (crop circles, corn mazes, geopainting, etc)
- others?

I'd like to get a number of opinions before I make changes in this area. Suggestions welcome!

#9 Tim Osborn

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Posted 21 April 2006 - 06:50 PM

I couldn't get multiple quotes to work in the body of 1 reply, so the following looks a little messy.

Quote--------------------------
"I looked at the PLSS lines on the topo map at that point, and even there where they started, the lines are about 1.0 to 1.5 degrees off a true bearing, as calculated in ExpertGPS. I suspect that this is a result of newer Earth models (datums and ellipsoids) since 1815."
---------------------------------

Perhaps. Also, the equipment wasn't as good in 1815 and surveyors do make mistakes. However, the bottom line is that the orginally surveyed lines are the legal delineations even if later found to be in error. Also, the range and township lines get less true the farther you move away from the Principal Meridan and the Baseline. That's why every 24 miles east-west of the Meridan and every 24 miles north-south of the baseline so called Correction Lines were established to get things back to true.

Quote--------------------------
"I was worried I was going to mis-type a bearing and distance along the way and have to start over. It would be nice to be able to enter everything into Excel or a similar data grid, and then paste it into ExpertGPS."
---------------------------------

I agree. These lists of deed calls can get very long. Anything that would reduce the chance of error or omission would be a good thing. For a simple data entry interface for deed calls you might want to take a quick look at http://www.genealogytools.net/deeds/. Note the variety of distance units that can be used and the fact that more than 1 unit can be used in a call (e.g. 5 chains plus 6 links). Also, Surveying Units and Terms are defined at http://users.rcn.com/deeds/survey.htm.

Quote--------------------------
"I'm trying to envision a "Rotate Selected Data" tool in ExpertGPS. What else could it be used for? Are there other reasons to have it, outside of this kind of property description?"
---------------------------------

What if someone entered a lot of data, say via Project Waypoint, and then realized the data was based on magnetic observations. Instead of having to manually recalculate the data and re-enter, they could just rotate it in ExpertGPS by the appropriate magnetic declination.

Quote--------------------------
"I can think of a few areas where the ability to import a list of azimuths and distances would be useful:
- property descriptions
- setting up regularly-spaced sampling grids for a scientific survey
- creating geometric shapes (crop circles, corn mazes, geopainting, etc)
- others?"
---------------------------------

Orienteering? I don't know because I don't compete in Orienteering.

If someone didn't have a GPS unit, they could still create routes and maps in ExpertGPS with nothing more than a list of compass bearings and paces (after they determined the length of their pace).

I think this would be a very useful capability.


Thanks Dan.

Tim

#10 Tim Osborn

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Posted 17 May 2006 - 11:23 PM

Back in April, Dan was interested in additional opinions concerning changes and new features that would make it easier to do things like plot property boundaries (legal descriptions in deeds) in ExpertGPS. With all the new members that have joined the forum in the past week or so, you may not have seen this thread. If you're interested, take a look at the earlier posts in this thread and contribute any related ideas or opinions you have.

Tim Osborn

#11 Chris Catron

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Posted 19 May 2006 - 10:57 AM

Funny thing just happened. A co-worker came into my office and asked me if there was a way to rotate a shapefile in expert GPS slightly to match up with the edge of a roadway shown on the Aerial photo. Then I opened this thread....

There are times when it would be helpful to be able to click a shape and rotate it slightly to match up with known features when the end product is only intended to be a general representation of boundaries. Typically we use a consumer grade hand held GPS to record a track of Wetland boundaries then download that track and convert it to a shape. We thus get a pretty good representation of the size and general shape of the wetland but due to the inherrent inaccuracies assocated with the handheld not being left on a point to average for an extended period of time, the shapes are often shifted slightly off their actual location. Not a big deal since meets and bounds survey of flagged boundaries will be eventually conducted anyway by a lisensed surveyor - What we are after is usually just a good map showing approximate sizes and boundaries. Being able to nudge and rotate would be great.

#12 Dan Foster

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Posted 19 May 2006 - 01:12 PM

Can you send me (support2006@expertgps.com) a file with real data that you'd like to be able to rotate?

#13 Chris Catron

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Posted 19 May 2006 - 03:30 PM

The file in question has already been re-drawn manually. I'll try and find something I can send.


For illustration purposes though, just think of a square pond located next to a roadway which travels north/south along the eastern edge of the pond. In the field, we know the east boundary of the "pond" is against the toe of the north/south running road. When we get back and plot the points on an aerial however, for some reason, the top of the Square pond is slightly further from the road than the bottom I just want to twist the pond a little to make it fit what I know is real world. Obviously with a square, I'd just move the points on top. but with a complex shape, it would be easier to do it automatically.

Chris.

#14 Tim Osborn

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Posted 19 May 2006 - 05:41 PM

Dan:

I'm sending you a gpx file with a property boundary that needs to be rotated a little clockwise. The SW corner of the property is in the approx correct position, so this is the point around which the rotation needs to occur. You will know when you have rotated it enough.....the NE property lines will run approx down the center of the river in the aerial photos.

In the track description it says the NW property lines need to run down the center of the river, but its actually the NE property lines....obvious when you look at the track over the aerial photo.

Tim

#15 Carl L Hurst

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Posted 19 May 2006 - 06:28 PM

Tim,
I know you can create the property shape(s) "in house" from legal descriptions before, or instead of, going out into the field. Or you can go out into the field and get GPS data and come back in and plot it. ...and I know that sometimes it doesn't match up with "modern" maps and APs
Wouldn't I be correct in assuming that if you have GPS coordinates for corners or other obvious points, and that "selected shape"was rotated, then the new Expert GPS corner coordinates would not match up with actual "on the ground " data?

I have the same problem with plotting irrigation ditches from old ditch plats.

Sometimes it's surveying error , sometimes it's map error (seems like the map is actually what needs to be rotated), but most of the time it is just the changes in equipment and techniques over the last 100 yrs since the original survey.

Also,I have found that in the case of using PLSS data, you can't assume that it is necessarily correct. A lot of the PLSS data in my area was done using "projection" and there are cases where it does not agree with what is on the ground.

Carl

#16 Tim Osborn

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Posted 19 May 2006 - 10:26 PM

Wouldn't I be correct in assuming that if you have GPS coordinates for corners or other obvious points, and that "selected shape"was rotated, then the new Expert GPS corner coordinates would not match up with actual "on the ground " data?


Carl:

I would agree with what you say, assuming that the coordinate-based data you were rotating were of high accuracy. If they were produced with a consumer-grade gps receiver, then the "on the ground" data probably wouldn't be so accurate that I would worry too much about the coordinate changes from a bit of rotation, depending of course on your intended use.

I think you need a pretty good reason to rotate, however. Like when in a legal description it says that a property line runs down the center of road and the plotted representation doesn't, or if you plot several adjoing properties and they don't fit together. Just because a plotted boundary line doesn't track a fence line visible on an aerial photo probably isn't a good enough reason. The fence may be in the wrong place.

The kind of things I've been doing are plotting property boundaries from deed descriptions "in house" and then viewing them against aerial photos...not in any legal sense but mostly to help others get a sense of what is involved when the Highway Department wants another piece of a property to widen the highway, or there may potentially be a boundary dispute with a neighboring property owner. In both cases Licensed Surveyors will do the real on-the-ground work, but my experience is that all the landowner ever receives is a written legal description...and few people can look at a bunch of bearings and distances and understand what it really means. A plot on top of an aerial photo, even if a little inaccurate by modern survey standards, makes clearer what is involved and serves as a rough double-check against surveyed results.

Here in Northwest Arkansas, the Regional Planning Commission has been producing aerial photos (DOQ's) annually for the past several years. The ones taken in late 2005 are stunning high-resolution (1 foot per pixel) color photos. In the city you can even make out man-hole covers in the streets. I have been bringing these in as scanned maps in ExpertGPS.

The properties I have plotted are ususally out of rotation by only a degree or two or less, and its not entirely clear to me why. Of course there is the potential for surveyor error and changes in techniques and accuracy over the years as you pointed out. And, there's always the potential that the bearings in the description are magnetic bearings, but if that were the case one would expect a much larger degree of rotation. In ExpertGPS all bearings are True, so magnetic declination is not an issue within the program. In the area I work in, UTM grid declination is about .75 degrees West and State Plane Coordinate declination is about 1.35 degrees West, but neither of these should matter either for plotting bearings and distances [as long as you are sure that the bearings you have are geodetic bearings (i.e. use true north as the basis of direction)].

PLSS corners seem to be a paticular problem to me as well. The corners and lines on topo maps don't seem to be very accurate and the GCDB lat-lon data you can get online from the BLM is partially taken from the USGS topo maps plus other data and then subjected to least-squares regression. I haven't found it to be very accurate either, at least for what I would like to do. Also, unfortunately here in the city, most of the PLSS corners have been obliterated or lost...that's less of a problem outside the city.

Tim

#17 Dan Foster

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Posted 08 June 2006 - 05:29 PM

I made a fix in ExpertGPS 2.3.4b4 that increases the accuracy of the Project Waypoint dialog (it was truncating bearings to a tenth of a degree). Tim's property boundary above still is off by a bit, but I was able to get a good fit simply by moving the entire boundary - no rotation needed.

The new beta: http://forums.topogr...p?showtopic=163

#18 Carl L Hurst

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Posted 08 June 2006 - 06:42 PM

Dan,
When getting into plotting property boundries, as Tim and I both have mentioned ,it would sure be nice to have an option for Quadrant bearings.
As well as the multiple options for bearing format.




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