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Snowplows Suck for Disks


new_dharma

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th_2726_C1.jpgth_2726_C.jpg

I just started looking for benchmarks a couple of days ago...I found one near a cache of mine. Reading the data sheets for the 4 I have found is interesting, because 2 were in the correct spot, but the other 2 were off a bit...then I noticed the dates on the bridges...they are almost 20 years newer (and probably wider). They were in the middle of the sidewalk...and being in Minnesota, they plow the sidewalks!

 

I made a note on the NGS site, but should I contact the Vertical Control Mark Commissioner (if we have one) or MnDot?

Edited by new_dharma
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new_dharma -

 

Nice finds! I guess they should've recessed those just a bit when installing them. :rolleyes:

 

By the way, all 4 of the marks you have found are horizontally scaled marks, so they will not necessarily be at the coordinates listed on the datasheet. If you like finding benchmarks and haven't done so already, you might wish to read the benchmark hunting FAQ, and in particular the place in it where it talks about coordinates being off. (I don't recommend notifying the NGS or the MNDOT that the marks are not exactly where the coordinates say they are since they would naturally realize that since they are horizontally scaled marks.)

 

If you like, you could note in your logs (both in Geocaching and at the NGS) the lat-lon coordinates you measure with your GPS receiver for any horizontally scaled marks you find. Do not do that for horizontally adjusted marks, however, since their listed coordinates are much more accurate than your GPS receiver can measure.

 

Welcome to benchmark hunting ! <_<

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the first I found by mistake...the 3 others (including the 2 damaged ones) i used the description...the "being off a bit" from the description had both the damaged disks "IN THE SOUTHEAST CORNER ABUTMENT OF THE BRIDGE" and now they are in the middle of the sidewalk...both bridges were widened since the benchmarks were placed in 1979.

 

i've looked over the FAQ/Before you Start/Read This section...i'll start using the descriptions and hitting the ones near my house.

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If the disks were described as being in a bridge but you found them on a sidewalk you have definitely not found the disks described--these are probably resets from when the bridges were rebuilt that never made it into the NGS database. There is a chance they were never surveyed to and never got marked. Pennsylvania has a lot of bridges that were replaced in the 1990s with blank disks on them.

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Perhaps those 2 disks were 'rubbed out' so that they would not be used instead of being ruined by a snowplow. There might be an odd history about them. Perhaps they are actually the original disks but moved to a different spot and the old designation filed off.

 

With benchmark logs, it is always best to provide 2 pictures for each mark found - a closeup, and a 'distant' shot which has the disk clearly in view but shows how it is situated with its surroundings. (Extra points for including an item named in the location description! :ph34r: ) In the particular situation of the 2 'rubbed out' disks, such pictures would be very good.

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Are the scratch marks in the expected direction of travel for a snowplow? If so, I'd accept that explanation.

 

Here are GC links to marks in the area, for convenience of other readers:

QO2070 2726C3 found good

WO2071 2726C2 found good

QO2072 2726C Replaced by scraped disk in sidewalk

QO2073 2726C1Replaced by scraped disk in sidewalk?

QO2074 2726B no GC log

 

And NGS data sheets

QO2070 QO2071 QO2072 QO2073 QO2074

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