Topographic mapping exercise...need advice

With total stations, field data is generally recorded as direction (azimuth or angle) and horizontal and vertical distances. Coordinate-geometry (COGO) software can then be used to reduce it to X,Y,Z coordinates to plot on a map or drawing.

Newer total stations can compute coordinates internally. I don't know whether the 203 can do it. To make that work, however, you need to decide in advance what coordinate system to use. That's a fairly complicated question in this case.

From online information about Xmap, it looks as though it contains a built-in base map that probably covers the entire U.S. That map has its own coordinate system based on latitude and longitude. It also looks as though the software can convert between lat-long and some local coordinate systems, including state plane and UTM.

To get your field data to show up in the proper place on the base map, you would need to tie into one of the coordinate systems that Xmap supports, such as state plane. You could shoot two or more local control monuments, state or USGS, with known state plane coordinates. The nearest ones might be several miles away. Or you could get handheld GPS positions on some of your points. Those positions might be accurate to within 50 feet or so.

After doing that, you might find that the Xmap base coordinates were not that accurate in the first place. Your field work could show up hundreds of feet out of position relative to the base map.

GIS maps and GIS software are not intended for surveying work. Using Xmap or any other GIS software to plot a topographic survey is like trying to drive nails with a screwdriver. I think you need something different. I don't have any recommendations, but others on this forum most likely will.

> With total stations, field data is generally recorded as direction (azimuth or angle) and horizontal and vertical distances. Coordinate-geometry (COGO) software can then be used to reduce it to X,Y,Z coordinates to plot on a map or drawing.

Thanks. That helps a great deal. The 203 WILL do COGO, but my intention was to create a strictly local coordinate system...based on one known (and very recently surveyed) point and edge of the property...not tied into the SPG at all. For now, as long as the points I map are all where they are relative to each other, I'm fine for now). I thought the math and plotting would be easier if it's already reduced. BTW, I did check to see where the nearest USGS horizontal control point is; it's 3 miles away!

> GIS maps and GIS software are not intended for surveying work. Using Xmap or any other GIS software to plot a topographic survey is like trying to drive nails with a screwdriver. I think you need something different. I don't have any recommendations, but others on this forum most likely will.

Understood completely. I just haven't (yet) invested in any of the true CAD based surveyors' packages, and budget may not allow. For now the principal challenge is gathering the data according to generally accepted practices. I can always use the data again later (if it's done right).

As for the nuts and bolts of file types and formats: I should have (and will) put that in a completely separate thread, as it's pretty unrelated to the surveying technique question.

Thanks again.

My guess is your attempts to wedge cogo information into XMap will only result in utter hair-pulling.

why not try it old school first?

Using the topcon and a paper/pencil field book - do the survey, recording angles right, vertical angles, and slope distances.

Then plot the sideshots out on graph paper using a compass and scale (ruler.)

then draw the lines connecting each point into an irregular triangular network.

Then draw the topo contour lines.

What this will do is give you a better understanding of what all the whiz-bang technology that we use actually does, and most likely appreciate it much better.

trying to do a topo plan in xmap would be JUST AS LABOR INTENSIVE, and would likely not be producable anyways, due to the inordinate amount of coordinate transformations that you'd have to do.

I know plenty of licensed, professional surveyors who would fall into the fetal position if someone asked them to do this.

Very good advice - Old school..I like it.

> why not try it old school first?

I'm totally good with that. Last time I did this (won't say how many years ago), I did it with a Plane Table and Alidade. Not afraid of old school.

>
> Using the topcon and a paper/pencil field book

I know what one of those is. Got one (and know how to use it).

>
> I know plenty of licensed, professional surveyors who would fall into the fetal position if someone asked them to do this.

I'm a glutton for punishment. Stay tuned.

😀

Mr. Bailey is right. Try the old-school methods. They still work, and you'll get hands-on experience with the things that modern software does automatically.

A local, assumed coordinate base would be far and away the easiest to work with for what you are doing.

Before starting to capture coordinates (or angle and distance) to topo points with a total station, it would be best to run a control traverse, check its closure, and adjust it. Then you would have adjusted coordinates for your control points to input into the TS at each setup, and field error would not be carried from one setup to the next.

It would most likely be possible to use the TS to carry coordinates around the control traverse and back to the starting point, although I haven't ever done it that way. The difference between initial and final coordinates for the starting point would give you the closure error.

It's definitely possible to run a traverse by recording angles and distances. That also enables you to read the closing angle, and add up and adjust the angles in the figure. As far as I know, carrying coordinates in the TS would not allow you to check the closing angle or make any adjustments in the angles.

In either case, a handheld calculator with trig functions would work for traverse adjustments and manual coordinate calculations. I don't know what type to recommend among the present-day models. I use a 30-year-old HP 11C.

You'll need an elevation on each control point. The best and most trouble-free method would be to run a loop with a level and rod. These would not be very expensive if bought used, and would be handy later on for any grading you might want to do.

Trig levels with the TS would also work, but would require more calculations, and extra field work to compensate for errors.

Another possible trick

Need Google Earth (not Google Maps) it's free
Need NGS CorpsCon, also free.
Need NGS INVERSE3D online version is great

There is another thread just posted regarding newer Consumer Grade GPS accuracy.
Appears to be (with WAAS) on the order of 5-10 feet one shot autonomous.
I'd select a good open local spot on your site, at a durable, maybe Google Earth ID'able point, and do averaging for one or more hours.

That will give you a "fairly" good "where am I" point in Lat-Lon WGS84

To orient your location (in an Azimuth sense) pick the farthest Google Earth ID'able object you can see and be able to turn an angle to from your "where am I" point.
Radio tower, church spire, building corner, etc
Pick off the Lat-Lon for that point in Google Earth.
If it's far enough away (as in several miles) Lat-Lon error won't affect Azimuth too much. Good enough for this crude method.

INVERSE3D the two points. That's your reference Azimuth.
CorpsCon will translate Lat-Lon to applicable "pseudo" State Plane coordinates at "where am I" point.
Don't worry about WGS84 vs NAD83 stuff now.
Where I'm at in SoCal it's 4.1ft NW-SE diff.

Get an angle at your "where am I" point from AzRef point to a long leg in your local traverse. Everything is oriented off that line.
(there is an angular correction between SPCS and Lat-Lon that normally is applied.
In my area amounts to about one degree. Let's not deal with that here)

Survey as normal with Plane Surveying angle dist. Generating "pseudo" State Plane coordinates

Finally, feed all your pseudo "State Plane Coordinates" batch style to CorpsCon to get Lat-Lon for all points. There are several ways to feed these into Google Earth or Maps or XMAP.

If nothing else it's a way to detect busts in your survey.

Also remember Google stuff isn't perfectly projected.
I think it only uses nearest 0.1 second of Lat-Lon so maybe off maybe 5-10 feet.
And that you are not generating proper accurate State Plane Coordinates.

PS
*)Some Radio Towers etc actually have NGS Datasheets with exact coordinates.
Very old school way of orienting a local survey.
But check with Google. Near me a prominent Radio Tower had been rebuilt
in a slightly different location after an airplane hit it. About 100ft
NGS still had old values!

*)NGS software carries all the decimal places of precision.
This is an unknown in much software out there and can generate big rounding errors.

Wow! That's a lot of cool stuff. I'm taking it all under advisement.

> That will give you a "fairly" good "where am I" point in Lat-Lon WGS84
>
> To orient your location (in an Azimuth sense) pick the farthest Google Earth ID'able object you can see and be able to turn an angle to from your "where am I" point.

Since I truly am (for now) interested only in local coordinates, I think I have enough information to do what you're suggesting. A licensed surveyor recently surveyed the property "next door", and there is a corner of the adjacent landowner's property that is common to ours, with an azimuth.

His survey says:

"Bearings on this plat refer to Vermont Grid North as established by OPUS observation using Topcon Hyperlite + GPS receivers. Conversion =-0 degrees, 03'"

So, if I have both a point of beginning and an azimuth to start from, can't I take this to the bank? I mean, he IS licensed after all.

Because he never placed them on the earth (or at least not on his survey), I've placed the corner in Google earth, by sighting from that point to two concrete bridge abutments and a power pole, both visible in google earth and Xmap (to within perhaps 5 tenths of a foot, which, for my purposes should be good enough, no?

> There are several ways to feed these into Google Earth or Maps or XMAP.
>
Yes, I'm good there. I have a way to translate metes and bounds to lat/long and can gpx in and out of both Xmap and Google earth.

That said, I'm assuming that, for a property measuring less than 25 acres or so, if I have the Lat/Long of a single point, and a good azimuth, all the others will be close enough for mapping purposes.

Let me know if I'm going astray here. As always, I'm learning that the more I learn, the more I learn what I've yet to learn.

Looks like you are well on your way.
Neighbors point was a lucky thing.