Wild T2

In the lower left corner of a USGS quadrangle sheet are the credits. On most, but not all, maps is a line that starts with "Control by". It is followed by the agencies whose control is shown on the map. In my area, this is true for the older maps, but more recent map revisions have a statement saying that the survey control [is] current as of the date of the previous edition.

I have seen short witness posts on marks at airports. I assumed that they cut off the top section of a standard post to protect aircraft that may taxi near the mark. It is possible that the property owner may not have wanted a full length orange post on their property. A cut down post may not have been a problem.

Good control is just as important today as it was years ago. Sanitary sewer grades are usually built on a relatively flat grade. Good control helps to insure that it flows down hill. Just one of many modern applications.

You can report outages to the Coast Guard here... http://www.navcen.uscg.gov/gps/gpsuserinput.htm

Around here there are some USGS marks from 1928 that have NGS/USC&GS style designations (letter followed by number followed by year). Most post WW2 USGS marks use a number followed by the party chief's initials followed by the year. JZ1775 is an example from 1928 that was also tied in by NGS that used the NGS/USC&GS format. This may have been a short-lived USGS policy. Most agencies that set marks try to come up with a designation style that is unique to their agency.

Double sided steel tapes were used to measure the distance from the station mark to the RMs. Zero to 100 feet on one side and Zero to 30 meters on the other. The landmark intersection stations, the reference marks, and the azimuth mark were observed in daylight. A reference mark near the station mark would be difficult to observe from a tall tower. They tended to set them as far from the station mark as they could, but not beyond the length of the tape. Never have seen a mark with nails pointing to the other marks though.

Given these two comments from the description... ON TOP OF HOOVER DAM and STABILITY: D = MARK OF QUESTIONABLE OR UNKNOWN STABILITY I am sure glad that I do not live downstream of there.

Here are a couple of links to articles about military surveying and mapping. http://www.asprs.org/asprs/resources/grids/11-2001-ptsm.pdf http://www.profsurv.com/ps_scripts/article.idc?id=1218 And of course, thanks for your service over there.

Perhaps a groundwater monitoring well (MW 20 in the photo), but all of the monitoring wells that I have seen have a round well casing, not square.

Another satellite predictor from Leica. http://downloads.leica-geosystems.com/down...manac/index.htm Don't forget to keep your almanac file up to date.

NGS set two more Lewis & Clark marks at the Denver and Philadelphia mints. http://www.usmint.gov/pressroom/index.cfm?..._release&ID=494 http://www.usmint.gov/pressroom/index.cfm?..._release&ID=492 They recently started production of the new Lewis and Clark Nickels... http://www.usmint.gov/mint_programs/index....n=nickel_series

Photo of a nearby historical marker from the 1950's. http://www.photolib.noaa.gov/historic/c&gs/theb1561.htm If you want to visit the origin of the NAD'27 datum you can go to Kansas. You will have a devil of a time visiting the origin of NAD'83. Its at the Earth's mass center.

Did the "GPS Sticks" look like this? http://www.schonstedt.com/products/magneti...cx-ga72cd.html# If so they were looking for the survey marker at the center of the aerial target. Also, as highways get re-paved some localities preserve the original mark in a steel monument box below the present day road grade.

Still very important to surveyors and civil engineers. It can keep things like this from happening. http://www.nos.noaa.gov/news/features/imag...rokn_bridge.jpg Yes the picture is a fake. Here is the full web page. http://www.nos.noaa.gov/news/features/welcome.html

The surveying instrument that he ran the line with is at the Smithsonian. http://americanhistory2.si.edu/surveying/o...rdnumber=758993

This diagram indicates that the subsurface mark should be four feet below the surface. http://img.Groundspeak.com/user/88694_600.jpg I have found only about four or five subsurface marks while surveying. All of them were only about 2.5 feet below the surface. Thats about the length of an adult mans arm.

I have found aluminum USGS discs from that time period. In my case it was set in 1957. What happens sometimes is that new construction is going to destroy a mark. The contractor obtains a replacement disc from the USGS but it was somehow forgotten about and never tied in by USGS or NGS. We frequently give discs to contractors on bridge replacement jobs. We keep a record of it and will tie it in when the next time that we are working on that stream, which might be several years. I am also sure that we have a bunch of them that we have forgotten about as well.

The new marks are at the Falls of the Ohio State Park in Clarksville Indiana. http://www.in.gov/dnr/parklake/parks/fallsofohio.html Its about a one mile hike along the levee from the Intrepretive Center to the boat ramp.

There are actually two disks. A large one near the Intrepretative Center and a smaller one near the boat ramp. Both have the same design on them. http://img.Groundspeak.com/user/88694_500.JPG William Clark was staying with his older brother George Rogers Clark when Lewis arrived with the boats and supplies. Of course big brother George was also a major figure in US history.

I was at the USGS Mapping Center in Rolla in September 2000. There was very little security at that time. I bet things are different now. Here is a link to their web site. http://mcmcweb.er.usgs.gov/

I think that many of the depressions are the result of frequent use by surveyors. The first surveyor digs the mark up, uses it, and fills the hole back up. But some of the soil is lost in the process. Repeat enough times and you will be slightly building up the area around the hole with the lost soil and leaving the depression. We have sometimes borrowed soil from somewhere else or used play sand from the lumberyard to fill in the depression.

The next time you visit a State Park, stop by the Nature Center and ask the Park Naturalist to go out in the woods with you and show you some. The best place to learn how to ID plants is in the woods.

NAVD88 MILE HIGH BENCHMARK CEREMONY COLORADO STATE CAPITOL, WEST STEPS SEPTEMBER 29, 2003, 10AM Governor Owens will be dedicating the new Mile High Benchmark. There is already a mile-high bench mark on the capitol. It is at an elevation of about 5280 feet using the National Geodetic Vertical Datum of 1929 (NGVD'29), but is only about 5277 feet using the North American Vertical Datum of 1988 (NAVD'88). The new mark will be at 5280 feet NAVD'88. I guess Denver didn't want the nickname as the "Three Feet Short of a Mile High City"

With the info on the datasheet and the NGS program "FORWARD" from the geodetic took kit on their web page you can caluclate the latitude and longitude of the reference mark. Output from FORWARD Ellipsoid : GRS80 / WGS84 (NAD83) Equatorial axis, a = 6378137.0000 Polar axis, b = 6356752.3141 Inverse flattening, 1/f = 298.25722210088 First Station : Wisk ---------------- LAT = 46 59 7.64149 North LON = 123 49 29.15546 West Second Station : WISK RM 1 ---------------- LAT = 46 59 8.01885 North LON = 123 49 29.24593 West Forward azimuth FAZ = 350 41 0.0000 From North Back azimuth BAZ = 170 40 59.9339 From North Ellipsoidal distance S = 11.8090 m

A few more examples... http://img.Groundspeak.com/user/88694_200.JPG