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fourteenthstreet

how to find latitude and longitude

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Hello,

This forum helped me out a lot a couple of months ago for a project i was working on about street infrastructure. This is now going to be part of an exhibit of sorts about the perception and interaction of a street in new york city. For my part of this project, I need to find the exact longitude and latitude of the horizontal control point that my students and i found. any tips? online tools? for free?

thank you for any help and information!

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Hello,

This forum helped me out a lot a couple of months ago for a project i was working on about street infrastructure. This is now going to be part of an exhibit of sorts about the perception and interaction of a street in new york city. For my part of this project, I need to find the exact longitude and latitude of the horizontal control point that my students and i found. any tips? online tools? for free?

thank you for any help and information!

I assume you are looking for points that do not appear in the Geocaching or NGS databases. Depending on your needs, you may find the USGS GeoPDF topo maps useful. With the aid of a plug-in, these maps have been corrected so that you can get excellent latitude and longitude data (though I don't see a clear description of just how accurate the positional data is).

 

Here is a good explanation of how the GeoPDF maps work.

 

Good luck!

-ArtMan-

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Hi, Art,

 

I tried the link but it says "session expired". Can you give us more info?

 

-Paul-

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fourteenthstreet:

 

You need to tell us what you mean by "exact latitude and longitude." Exact to the nearest .04', exact to the nearest foot, nearest meter?

 

Assuming you can't find published horizontal coordinates for the point in question, you could do any of the following:

 

If you precision requirements are only to the nearest 10 feet, you could obtain acceptable Lat-Long coordinates by standing on the point with a handheld consumer GPS receiver with WAAS capability, assuming the sky is not blocked by trees or nearby buildings. Using the averaging capability of the GPS receiver will improved the results.

 

If your precision requirements are sub-meter you could probably borrow a mapping-grade GPS receiver and occupy the point as above.

 

If you require greater precision than sub-meter you are getting into the province of the surveyor who could occupy the point with survey-grade GPS equipment or traverse to the point from known horizontal control using a total station.

Edited by tosborn

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I suspect his purpose would be satisfied with the values from one of the on-line map services, which could be read out to 10's of feet, i.e. degrees, minutes, seconds to tenth seconds and the tenth seconds within a few digits. I doubt he cares which datum, but may want to take note of the datum. I'm not current on which services are good and offer lat-lon values.

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We can't tell from your post whether your mark is a private cadastral mark or maybe something set by the city, which does maintain records of such marks as the disks you often find in sidewalks in New York. You might start with Public Works, if there is likely to be a public record. If it's a property corner, the earlier suggestions will be best.

 

Cheers,

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Hello,

This forum helped me out a lot a couple of months ago for a project i was working on about street infrastructure. This is now going to be part of an exhibit of sorts about the perception and interaction of a street in new york city. For my part of this project, I need to find the exact longitude and latitude of the horizontal control point that my students and i found. any tips? online tools? for free?

thank you for any help and information!

I have found flash earth to be fairly accurate for finding coordinates, although I don't know your definition of exact.

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Margot

 

From Google Earth I got the following coordinates for the SW corner of 14th St. & 2nd Ave.

 

N40 43.939 W073 59.108

 

The cursor coordinates show up in the bottom left corner and update as you move around.

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Margot

 

From Google Earth I got the following coordinates for the SW corner of 14th St. & 2nd Ave.

 

N40 43.939 W073 59.108

 

The cursor coordinates show up in the bottom left corner and update as you move around.

 

thank you! i got something very close

(Lat: 40:43:59N (40.73312)

Lon: 73:59:02W (-73.98379)

of course, what exactly does "close" mean?

 

your quote is great... going to kipling. thanks.

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What does close mean?

From Holtie's N40 43.939 W073 59.108 = N40 43' 56.3" W073 59' 6.5"

to

Lat: 40:43:59N (40.73312)

Lon: 73:59:02W (-73.98379)

is a distance of 133.3 meters = 437.5 feet northeast (az 52 deg and a hair)

 

(Assuming you are in the same datum; NAD27 and NAD83 differ by about 37 meters=121 feet here)

 

I would have expected agreement within 100 feet if two people read out the same feature on the map.

 

(edit: corrected units)

Edited by Bill93

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What does close mean?

From Holtie's N40 43.939 W073 59.108 = N40 43' 56.3" W073 59' 6.5"

to

Lat: 40:43:59N (40.73312)

Lon: 73:59:02W (-73.98379)

is a distance of 133.3 meters = 437.5 feet northeast (az 52 deg and a hair)

 

(Assuming you are in the same datum; NAD27 and NAD83 differ by about 40 feet here)

 

I would have expected agreement within 100 feet if two people read out the same feature on the map.

 

yikes, that seems like a lot of space. i think i may flag a cab with gps, get in, ask for the reading, pay the driver for the favor and be more precise!

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I have found by looking at triangualation stations in the NYC area that the accuracy of Google Maps satellite views are very close, within a few feet. Look at this one for station Mansion 2 in Queens: Google Map of KU3822

 

Look at the little white spot in the grass where the pointer is sitting. That's a 2 foot concrete post where the station is set. Here is my picture of the station:

 

KU3822 GC log

4f72a0d0-e35f-476b-b583-204781ccf642.jpg

 

I have seen similar accuracy in the New York area. Note that Google goes to a scale of 20 feet (lower left of map) which is one level higher than most maps (50').

 

Bottom Line: Forget the Cab. Use Holtie22's numbers. The Cab's GPS (or your GPS) will not be nearly as close as Google.

Edited by Papa-Bear-NYC

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I also checked with Google Earth, using the location-adjusted mark that Papa-Bear-NYC showed.

I have Google Earth set for DDD MM SS.SS mode (tools, options, 3d view, show lat/lon) and find that I can move the mouse in 0.01 second increments as shown at the bottom of the Google Earth screen. This is a PRECISION of 0.01 second. My GPS receiver (and I assume all of ours is the same) has a precision of 0.1 second. (My car GPS receiver has a precision of 1 second).

 

In order to check the ACCURACY, I looked at the KU3822 mark with Google Earth and placed the little hand icon over the location of the mark. The reading I got was:

40 47 37.39

73 31 10.52

the "original datasheet" for the mark has the adjusted location:

40 47 37.37909

073 51 10.49892

The difference is only 0.01 in latitude and 0.02 in longitude !

I don't know if Google Earth has this level of accuracy consistenly, but if it does, it's both more precise and more accurate than the GPS receivers we use.

 

In the area of KU3822, using the Google Earth ruler and watching the coordinates at the bottom of the screen, a 0.1 second longitude difference is 7.6 feet and a 0.1 second latitude difference is 9.8 feet. This is the precision level of our GPS receivers but their accuracy is somewhat less - a radius of 10-15 feet or something like that.

 

I reach the same conclusion as Papa-Bear-NYC !

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14th Street, I would hesitate to use the word "exact" on your web site. No survey coordinates are exact, all have some error. The error may be very small or much larger, but there is always some error.

 

GeorgeL

NGS

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14th Street, I would hesitate to use the word "exact" on your web site. No survey coordinates are exact, all have some error.

"14th", how about "specific"? E.g., "The marker represents a specific point on the globe."

 

Also, a question for George: is it accurate to say that a geodetic control point can be used to establish property lines? Is that close enough for rock 'n' roll for "14th"'s project, or should he/she differentiate between geodetic and cadastral marks? In the case of a mark set by the city, might it be used for both purposes?

 

Patty

 

[i added the following on 7/11]

 

p.s. Forgot to mention that, for accuracy, it would be good to either put "N" and "W" on the coordinates, or to precede the longitude with "-". A bit more space between the two sets of numbers would be helpful, too, to clearly separate them. Sorry for all the little suggestions, but I'm a writer, editor, and former graphic designer, so I can't help but think of stuff like that! :anitongue: Really, it looks like a fun project, so I hope it goes well.

Edited by Wintertime

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What does close mean?

From Holtie's N40 43.939 W073 59.108 = N40 43' 56.3" W073 59' 6.5"

to

Lat: 40:43:59N (40.73312)

Lon: 73:59:02W (-73.98379)

is a distance of 133.3 meters = 437.5 feet northeast (az 52 deg and a hair)

 

(Assuming you are in the same datum; NAD27 and NAD83 differ by about 37 meters=121 feet here)

 

I would have expected agreement within 100 feet if two people read out the same feature on the map.

 

Using two separate sources independent of Google Earth (the 1 meter resolution NAPP Digital Orthoquads, and the 2007 Tiger/Line dataset), I get the center of the intersection at N 40° 43' 56.444" W 73° 59' 05.791" within an expected accuracy of about a meter or two.

 

From estimation, I get the SW corner of the intersection (that description itself is open to interpretation) at N 40° 43' 56.324 W 73° 59' 06.261. My estimate is about 17 feet from Holtie's numbers.

 

Edit: For reference, here is an overlay of the Tiger/Line centerline (black and yellow line) on a Microsoft Virtual Earth image (yet another source of information), with my measured points shown as the yellow triangles. The overlay was done using the coordinates in the image and dataset, not by any manipulation or placement by hand.

 

ny14th2nd.jpg

Edited by holograph

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I decided to virtually visit Denver Colorado to look for another mark using streetview. I did find an adjusted station but it turns out I didn't need streetview (there's no road right there) and used a .kml file instead. People found the mark but didn't take a picture but it's pretty obvious on Google Earth, it's a white spot in the grass. I put the hand icon over the image of the mark's logo lid and got these coordinates:

39 47 04.34

104 58 53.46

I looked at the datasheet to find:

39.47 04.35

104 58 53.47

This is even closer than last time.

I also experimented with matching the taping with the ruler function. It didn't work quite as well as just putting the icon over the spot. It would be interesting to see a picture taken by someone to be sure that the white spot is the logo lid's location.

 

I tried a few more without success (couldn't get an image). Then I tried KK2099. It's dead obvious on GE. There's a couple logs with pictures, somewhat inconclusive, but showing a fair amount of cement around the mark. It's another one in grass - not too surprising for a horizontal control. I did the measurement with the hand and got

39 44 34.69

105 00 03.94

the datasheet (rounded) gives:

39 44 34.69

105 00 03.95

Try it yourself and see!

 

I tried some others and then tried AE5252. There's no clear indication of a mark except that it is described as being in the middle of 4 piers. I took a 'reading' at the center of the design. Once again the accuracy was extremely close. An interesting 1936 mark, it would be interesting to see a picture of it with the 4 piers.

 

Actually I'm a bit disappointed in Denver as there were no location-adjusted marks that could be seen with both GM-streetview and GE. So, although the results seemed good, I can't be dead certain of any of these 3 marks. There was also no really good 'distant' pictures for them. I guess I should try another town. :huh:

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Thank you for the editorial help! right, specific seems like a better term. and i got the information about the marker being used to designate property lines from an email from a new york city government engineer.

i'm still on the hunt to discover attribution (who put that there??) and am following up with the department of transportation, since they issue sidewalk permits. who knows, maybe they will have the answer.

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Hi, Art,

 

I tried the link but it says "session expired". Can you give us more info?

 

-Paul-

Paul,

 

Try this: Go to FreeGeographyTools.com and enter geopdf in the search box.

 

The page I was referencing will appear as "Downloading USGS Topo Maps In GeoPDF Format, And The GeoPDF Plug ..."

 

-ArtMan-

 

PS - sorry for the delay in responding. I've been offline for a bit.

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