Questions about PLSS markings on topo maps

[Wintertime]

I have a couple of questions about the red lines on this map:

 

 

Why are some of the section and 1/4-section corners marked with red "+" signs, while others aren't?

 

Why are parts of the vertical red line passing through Aspen Valley and the horizontal line below the valley solid, while most of those lines (and all the other vertical and horizontal lines on the map) are dashed?

 

Oh, and a question about the topo (not PLSS) markings: what does the "T" mean at the end of the elevation numbers of the hilltops?

 

Thanks!

Patty

[2oldfarts (the rockhounders)]

Good questions. I will be awaiting the answers.

 

I would also like to know why the top red line of section 28 is not at a right angle. And, why the top line of section 27 is not straight, or is that just a quirk of the Mac display?

 

Are sections not supposed to be like boxes? Squares or Rectangles, or are they often surveyed at odd angles?

 

Shirley~

[CallawayMT]

I have a couple of questions about the red lines on this map:

 

 

Why are some of the section and 1/4-section corners marked with red "+" signs, while others aren't?

 

Why are parts of the vertical red line passing through Aspen Valley and the horizontal line below the valley solid, while most of those lines (and all the other vertical and horizontal lines on the map) are dashed?

 

Oh, and a question about the topo (not PLSS) markings: what does the "T" mean at the end of the elevation numbers of the hilltops?

 

Thanks!

Patty

 

Patty,

 

This page will help you out: Key to Topographic Maps

and here is a good USGS .pdf document: USGS Topo Symbols

 

Basically the dashed section lines generally are used in unsurveyed or protacted areas while the solid section lines are in areas which have been surveyed. The red tick or + marks are put on corners which were identified with some sort of found monument or sometimes a fence corner.

 

I'm not sure on the T question.

 

CallawayMT

[+GEO*Trailblazer 1]

The + means that there is a Benchmark, PLSS Section Corner or found section corner.

 

None means there is the Original Mark (maybe)whatever that may be from the GLO Plats.

(GLO) General Land Office.

 

Dashed lines are uncertian and the soid lines means it has been surveyed.

 

I will have to look up T.

 

TOPO MAP SYMBOLS

 

That's 2 out of 3.

[Bill93]

The section lines were supposed to be due N-S and E-W, but if you consider the equipment, conditions, and pay for the original surveys in many areas, it is remarkable they are as good as they are.

 

I wouldn't want to try to hold a chain straight and level on a 15 or 20% grade, from sunup to dark, through underbrush with flies, snakes, and bugs after me, and camp for weeks in the wilderness eating biscuits and beans, all for minimum wage.

 

Sections are theoretically 8-sided figures, not 4-sided. The original survey in most areas set the half-mile points on the lines and if evidence of the original corner was found and perpetuated, that rules even if it makes a kink every half mile.

[Wintertime]

Thanks, all. I've seen the marks at two of the "+" marks; I'll try to look for the other two when I'm up there next month.

 

The explanations on the Univ. of Wisconsin site also brought another question to mind. I've noticed some "X" marks on topos that aren't marked "BM". I see now that that means there is a "recoverable mark," but not a "tablet." So what kinds of objects qualify as "recoverable marks"? A friend and I traipsed around an area off of Hwy 120 near Yosemite a couple of months ago, around a spot that had one of those "X nnn" designations, but we didn't find anything. Of course, not knowing what we were looking for, maybe we found it but never realized it. :-)

 

Patty

[foxtrot_xray]

Sections are theoretically 8-sided figures, not 4-sided. The original survey in most areas set the half-mile points on the lines and if evidence of the original corner was found and perpetuated, that rules even if it makes a kink every half mile.

Growing up out in the west-midwest, for the longest time I always thought the red lines were fence-lines. (My dad was big into maps, and back then would have 7.5-topos of the entire state rolled up in the back of his car.) At the time, I couldn't explain the red lines excapt to see that a fence was there. So, for the longest time, I assumed that the topos had fence-lines marked on them.

 

Now, continuing that ignornace, , I was under the impression that the non-"X"'ed numbers were just the high-elevation points for certain items. (Like in Colorado, the top of buttes.) While I've been to the top of buttes while growing up, I never remember seeing any 'marker' of some sort up there..

[Wintertime]

I was under the impression that the non-"X"'ed numbers were just the high-elevation points for certain items. (Like in Colorado, the top of buttes.)

I think that's exactly what they are.

 

While I've been to the top of buttes while growing up, I never remember seeing any 'marker' of some sort up there..

I agree--the ones that do have markers have horizontal control symbols (the little triangle) on the map, along with the elevation and the station name. If you just see an X and an elevation, I guess that means there's no "tablet," just a "recoverable mark," which I'm guessing could just be the top point of the hill.

 

Patty

[+Renegade Knight]

...Are sections not supposed to be like boxes? Squares or Rectangles, or are they often surveyed at odd angles?

 

Shirley~

 

They were laid out on paper in nice squares and rectangles. Then the field surveyor set the monument. The monument as placed became the real control for all subsequent property descriptions and not the nice clean paper version back at the home office. Some surveyors did better work than others. Some held true to the "close enough for government work" philosopy. The result is the distorted grid.

[Z15]

So what kinds of objects qualify as "recoverable marks"?

When you look at the old USGS notes and see a chiseled square, RR spike in tree root, punch mark in top of metal culvert, or similar mark noted as "UE" for Useful Elevation in the notes.

Edited June 5, 2008 by Z15