USGS topo map questions

[YellowHammer]

I used the old paper topo maps for finding secret fishing spots on our lakes and the Gulf of Mexico.  Old homesteads, ponds, humps, especially submerged roads were all gold.  I pored over them for hours, finding potential hotspots.  

Now, for bodies of water, everything is digital and updated almost daily.  In the marine world, the detail is often to 1 foot resolution, in 3D, and if the option is "turned on", every depth finder in the world with the capability, is linked via Skynet and anytime I drive over a spot, the new depths and details are uploaded (I have less than 1" target resolution on my units) and after so many units have uploaded data, the number are crunched by computer, maps are automatically updated and then automatically broadcast back to out to all the units, corrected for tide and water level.  All hands off, just takes a credit card to get the subscription service.  This is especially useful when dealing with shifting sandbars, fish aggregating devices, and obstructions.  Amazing technology.

[SwampDonkey]

For what I do, I only need basic stuff. Lengths, and area and a polygon. A weeks collecting is worth more than the GPS. :D All I get is a paper map with all the topo features and the boundary of the area to go measure on the ground. We use a fire grid system, so it is easy to locate any block to rough in a GIS boundary on computer to transfer to the GPS. My GPS has all the forestry roads, creeks, names and properties that you don't get when you buy a GPS. Get those from a government site and make my own custom map layers, which aren't GPX files. I can put aerials on the GPS, but I don't need them for anything. I'd use aerial photos on the GPS perhaps if cruising, otherwise nothing gained.

[caveman]

I used the old paper topo maps for finding secret fishing spots on our lakes and the Gulf of Mexico.  Old homesteads, ponds, humps, especially submerged roads were all gold.  I pored over them for hours, finding potential hotspots.  

Evidently one of our renters took my marine charts from our place at Anna Maria.  I had charts that I had been marking since I was a teenager.  I spent hours looking at those charts looking for spots like you are referring to.

[Southside]

Took me a second to figure out what you were saying there YH.  In my mind all I was thinking was why would there be topo lines ON the lake or the ocean.  :D

[caveman]

Back before I had a Loran or a GPS on the boat, we would leave from a known point, like the lighthouse on the point of Egmont Key and take a particular azimuth.  JMoore wore a watch and I'd watch the water pressure operated speedometer on the dash.  He would calculate how far we had been and let me know when we should be at our target destination.  We would set down and look at the bottom with a sonar flasher.  It is amazing that we ever caught any good fish or found the charted spots we were looking for.  

Now fishing is more like a video game, so I've been told.  It has been a while since I harassed the grouper or snapper.  

[YellowHammer]

It's just like a paper map, just more accurate and easy to visualize.  Here's the bottom geography of the Northern Gulf of Mexico, from the beach to the Desoto Canyon, which is the edge of the continental shelf.  Yellow is shallower, blue is deeper, the edge of the canyon is from 300 to 1,000 feet.  

 

 
 

  

[Old Greenhorn]

This is an interesting thread and I am enjoying reading along. Caveman made me think of one of the most unusual navigation techniques I have ever known of either on land or sea. Now I have learned both land and water navigation over 6 decades, was good at both for a fair part of my life, but have forgotten most of the finer points and details.
 We used to fish every year on the St. Lawrence Seaway, nest Clayton. Sitting in the boat everyday I got to watch a lot of lakers and other large vessels go by, even had to get out of the way of a few. Over the years I started reading and studying a bit about them and got some books written by local pilots and such. 
 When they make it through the locks, those Lakers pick up a river pilot who guides the ship through the river out to Lake Ontario, where he/she gets off and catches a ride back to do it again, or pilots a down bound ship out. Those pilots have their own marked up charts. They navigate by speed and time. They use a stop watch to time their progress at a given speed from landmark to landmark and the time to begin their turns as well as how many degrees they alter their course. (Those lakers turn slowly, so one needs to 'plan a turn'.)
 The seaway is a very difficult place to navigate a large ship. The depth can range from a few hundred feet, to just 39' or so (which is only a few few deeper than the ship's draft). In the shallow sections, if a ship moves too fast it can create a suction effect between the bottom of the hull and the bottom of the channel and suck the ship right down, grounding it. They also have to consider the water speed which is working against them up bound and pushing them faster down bound. The up bound and down bound speed limits are different for vessels over a certain length and draft. If I recall it was 5 MPH up bound and 7 MPH down bound, but these change each year based on river conditions and levels which can very a lot year to year.
 Also, some sections are only wide enough to barely allow passage of the wider ships. Navigation must be extremely precise. If a fog comes in the seaway can become extremely hazardous for these ships. One year we got socked in for a day and a night and when the fog lifted we saw ship and lakers in the oddest areas. They had managed to find some natural deep water outside of the seaway channel and anchor up, blowing fog horns from time to time and lighting their decks.

[Ianab]

Maps have always been fascinating to me too. I do like the newer digital versions, and the ability to locate yourself on them. A paper map is fine if you already know where you are, if you don't then it can be a challenge to get yourself orientated. If you have the local topo map saved on your phone, push the button and "You are here" appears, and it will tell you which way is North. As long as the map is saved, you don't need internet, the GPS and saved map data are there. 

This is the online topo map for NZ, centred on the farm I grew up on. I think it's only 15m (~50ft) gradations.  So it's not like Florida  :D

New Zealand Topographic Map - NZ Topo Map

But you can scroll around. zoom in and out over the whole country. 

[SwampDonkey]

Today's forest cover type maps are all online now. They say it's only for crown land, but it includes private lands as well. Shows boundaries, areas, perimeter and estimated standing timber volume in cubic meters/ha. I checked one stand on my property from their map. They have the volume pretty low, it's 2 to 3 x more wood than their estimate. I've actually cut off as much as their per ha estimate and there's a lot more wood than that especially back where the fir out number and out grow the spruce. :D

[Machinebuilder]

I love maps. I hate the movement away from paper maps.
I like having a big paper map spread out so i can see everything in between 2 places.

I also like my GPS, it can tell me where I am and I can usually find it on the map.

one App I have on my phone is Avenza, with it you can download USGS quads, including historical ones and MVUM for the forest service roads.
They are Georeferenced PDF's so the GPS shows where you are on the map.

On the USGS site you can get download the USGS Quads and historical ones. NO COST.

I used to play a photo tag game and one spot was a steam engine in the mountains. I got rather lost.
The latest map data (GPS and paper) came from 1963 USGS quads, since then several roads had been rerouted and closed.
I got stopped at a locked gate in a farmers pasture, looking at the road i wanted to be on.

I find it interesting to look at the historical maps, With the TVA lakes there are drastic changes before and after the dams closed

[Texas Ranger]

I got lost in Arkansas once using car gps, it kept wanting me to take gated roads through pastures.  I then used dead reconning and headed in general direction I wanted to go while the gps kept telling to take u-turns.  Got there. 

[SwampDonkey]

GPS maps preloaded I don't trust. They have roads were there never was one unless it was from the 50 or 60's or something. No sign of certain mystery roads or even plowed up berms. They don't have many forest roads on them, big gaps in data. The forestry stuff I get, at least exist, some aldered or flooded. I usually trace back from a work block to the main haul road because sometimes there are two ways in, but one not maintained. Used to sign forestry roads, but the signs are long gone.

[caveman]

 


8.  What are the double dashed lines on the map seen in section 36?
9.  What direction is the intermittent stream in section 36, just above T3n on the right side of the map flowing?
10.  What section number is the partial section shown below section 36?
11.  What is the highest elevation shown on the section asked about in question #10?
12.  What part of Florida is this quadrangle located, north, central or south?

[Ron Scott]

I have a number of nautical maps of the Great Lakes from the 1960's when I was actively shipwreck and underwater log hunting. We then started using them with the Loran when the Loran was developed. Some of my maps that have shipwreck locations on them have now become collectors' items and framed as large wall displays in lakeside bars and homes.

[caveman]

8.  What are the double dashed lines on the map seen in section 36?
9.  What direction is the intermittent stream in section 36, just above T3n on the right side of the map flowing?
10.  What section number is the partial section shown below section 36?
11.  What is the highest elevation shown on the section asked about in question #10?
12.  What part of Florida is this quadrangle located, north, central or south?

Furby is pretty good at the map questions, fellows.
Answers: 8.  Unimproved road (dirt road)
              9.  northwest, towards the lake.  The contour lines point to the source of the water.
              10.  section #1
              11.  178'
              12.  north Florida  The STR system in Florida is based off of the Prime Meridian Marker, which is located on the grounds of the old Capital, in Tallahassee.  Everything with a Township line denoted N, is north of that spot, Ranges denoted E, are east of that spot.
I did not bring any maps home, so I'll have to see if any of the pics in my gallery are clear enough to use for questions.

[SwampDonkey]

Your maps use pretty much the same symbology as ours. Our older maps will even show location of camps, farming community buildings or maybe hamlets with square dots for buildings. We have miles and miles of rural roads with buildings dotted along. They have started to put those symbols digitally on maps in the last couple years, for all buildings.

Locally, the army goes on orienteering and survey exercises on rural roads around here. I always see them carry paper maps.

[caveman]

 

Assume that the square B is in is the same size as the other three.  Write a legal land description for B (You will not be able to include township and range due to the poor resolution of the other pictures of this map).
13.  Legal land description of B
14.  How many acres is B?

[Ljohnsaw]

• 14 - 40 acres

[caveman]

Again, I apologize for the quality of the pics.  What I came up with is the nw 1/4 of the se 1/4 of the nw 1/4 of section 4 and it is 10 acres.  

[Ljohnsaw]

Hmm, guess I didn't look close enough. I thought it was 1/16 of a section, not 1/64. I see it now.

[caveman]

Generally, sections are divided, using this system into 1/2's and 1/4's.  A 1/4 is 160 acres, a 1/4 of a 1/4 is 40 acres, 1/4 of 1/4 of a 1/4 is 10 acres and a 1/4 of a 1/4 of a 1/4 of a 1/4 is 2 1/2 acres.  Any 1/4 will be ne, se, sw, nw, while any half will be n, s, e, or w.

At the bottom of these USGS maps is symbol that gives the magnetic declination from true north.  The declination varies depending where in the world you are.  I cannot make it out on the map pictured below, but let's assume it is 2 1/2° W.  

Question #15.  If the map shows 180° for us as an azimuth for us to follow to go from one point to another, what azimuth on our compass should we follow to not miss our mark?


  The magnetic declination information is right above the pink, photo revised information.  I can't read either on this picture.  A few other informative things can be found along the bottom of the map include revisions, scale, contour interval, location relative to the state, road types and the date the map was first made.

[Ljohnsaw]

Well, it's going to be one of the other. Never done this before. If you're saying it is 2.5°W, I would think that means you need to rotate counter clockwise that amount, so add?  Heading would be 182.5°.  Otherwise it should be 177.5°. eh, what's 5° off on a heading?😜

[clearcut]

This is a trick question.  Magnetic Declination changes over time.  According to NOAA's Magnetic Declination Calculator   the current magnetic declination for the area near Lake Jackson, FL is 5°9' W and changing Westerly at plus or minus 21' per year. 

As this is a Westerly variation, one subtracts the declination from the bearing. 180- 5= 175° should get you there. 

[SwampDonkey]

Declination matters if you're compassing. You always set declin. on the compass before compassing over land for that area your orienteering. If you're getting a bearing use the dial on the compass like protractor and put north at north on the map. Don't add or subtract decl. twice by mistake by adding it to the dial and then use a compass that is already dialed for decl. when sighting. The bearing is what the map says as if you were using a protractor. The compass accounts for the declin. if set properly. ;D A guy I know would always compass without setting decl., even without using the bearing from a map. Say go E with all the lines, well his lines were always off by the declination if he was running lines on the same block. You couldn't get that through his head. : It's fine if you're measuring area, the shape and area is the same but it's location if mapped is rotated without adjusting declination.

[caveman]

IJohnsaw is right.  I remember it as west is best and east is least, adding for west and subtracting for east, assuming plusses are better than minuses.