Author Topic: Determining True North  (Read 1784 times)

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Offline CW2274

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Re: Determining True North
« Reply #25 on: December 15, 2018, 04:37:00 PM »
Here's another wrench in the mix...I use magnetic north. ;)

Offline kbellis

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Re: Determining True North
« Reply #26 on: December 15, 2018, 09:13:43 PM »
I guess a .mp4 file cannot be uploaded, or at least I can figure out.  Anyone know how to do that?

Consider uploading it to YouTube or DropBox and post a link here.

Offline galfert

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Re: Determining True North
« Reply #27 on: December 15, 2018, 09:36:49 PM »
Nice job on the video. The narrating voice is very good also.

A kind word is always appreciated. Thank you Glenn.

Kelly

I'm not Glenn. I'm guessing autocotrect changed it.   :?:
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Offline kbellis

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Re: Determining True North
« Reply #28 on: December 15, 2018, 09:50:46 PM »
I'm not Glenn. I'm guessing autocotrect changed it.   :?:

So sorry, unsure now why I thought your name was Glen...

Offline galfert

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Re: Determining True North
« Reply #29 on: December 15, 2018, 10:11:35 PM »
I'm not Glenn. I'm guessing autocotrect changed it.   :?:

So sorry, unsure now why I thought your name was Glen...

NP. Name is George.
WS-2000 & WS-2902A | Ecowitt GW1000 | WeatherBridge (Meteobridge)
WU: KFLWINTE111  |  PWSweather: KFLWINTE111
CWOP: FW3708  |  AWEKAS: 14814
Windy: pws-f075acbe
Weather Underground Issue Tracking
Tele-Pole flag pole not up yet

Offline kbellis

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Re: Determining True North
« Reply #30 on: December 16, 2018, 08:26:33 AM »
@galfert - Nice to meet you George. I'm Kelly Bellis.

Offline kbellis

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Re: Determining True North
« Reply #31 on: December 16, 2018, 08:55:25 AM »
Seriously? The only thing I see in that pic is a street light....

Here's a tighter shot which has been enhanced in Photoshop from the same night:

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Can you spot Polaris now?
« Last Edit: December 16, 2018, 09:05:37 AM by kbellis »

Offline CW2274

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Re: Determining True North
« Reply #32 on: December 16, 2018, 02:43:18 PM »
Seriously? The only thing I see in that pic is a street light....
Can you spot Polaris now?
Phffft, I can't even find the Big Dipper, without that, forget it.

Offline kbellis

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Re: Determining True North
« Reply #33 on: December 16, 2018, 03:54:00 PM »
Phffft, I can't even find the Big Dipper, without that, forget it.

Here's a cheat for you:


Best viewed full screen HD on YouTube

Offline alanb

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Re: Determining True North
« Reply #34 on: December 16, 2018, 06:57:51 PM »
If you have a handheld GPS, especially one with waypoint averaging, you can use it to get a good approximation of true north from a given reference point.

Set your GPS to use decimal degrees for coordinates, then set a stake at the base location and use waypoint averaging to determine the coordinates of this base point. Now go north as far as you want (the farther the better, but within visual distance) to set a temporary reference point. Move east and west using the GPS readings to get the longitude as close as possible to the longitude of the base reference point and set a temporary stake at this location. Now use the waypoint averaging to determine the corrected coordinates of the temporary reference point. Compare the corrected (averaged) longitude to the averaged longitude of the base point and use this calculator (http://www.csgnetwork.com/degreelenllavcalc.html) to calculate the east/west distance correction that needs to be made at your latitude to get the longitude to match the base point longitude. Move the stake east or west as necessary and it should now be due north of the base point (within the GPS margin of error of course.) My Oregon GPS shows decimal degree coordinates out to .00001, and at 42 degrees N latitude .00001 is about 2.7 feet on a east/west measurement.
« Last Edit: December 16, 2018, 07:02:14 PM by alanb »
Alan

Offline CW2274

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Re: Determining True North
« Reply #35 on: December 16, 2018, 07:35:03 PM »
If you have a handheld GPS, especially one with waypoint averaging, you can use it to get a good approximation of true north from a given reference point.

Set your GPS to use decimal degrees for coordinates, then set a stake at the base location and use waypoint averaging to determine the coordinates of this base point. Now go north as far as you want (the farther the better, but within visual distance) to set a temporary reference point. Move east and west using the GPS readings to get the longitude as close as possible to the longitude of the base reference point and set a temporary stake at this location. Now use the waypoint averaging to determine the corrected coordinates of the temporary reference point. Compare the corrected (averaged) longitude to the averaged longitude of the base point and use this calculator (http://www.csgnetwork.com/degreelenllavcalc.html) to calculate the east/west distance correction that needs to be made at your latitude to get the longitude to match the base point longitude. Move the stake east or west as necessary and it should now be due north of the base point (within the GPS margin of error of course.) My Oregon GPS shows decimal degree coordinates out to .00001, and at 42 degrees N latitude .00001 is about 2.7 feet on a east/west measurement.
:shock:    I think I'll just keep using the North Star.

Offline SLOweather

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Re: Determining True North
« Reply #36 on: December 17, 2018, 08:39:35 AM »
One easy way I use to find true north is Google Earth. I found my location there, and looked for a landmark that was north of it.

Offline kbellis

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Re: Determining True North
« Reply #37 on: December 17, 2018, 10:25:40 AM »
One easy way I use to find true north is Google Earth. I found my location there, and looked for a landmark that was north of it.

Google Earth Pro is an excellent resource as it's free, has the Ruler tool  [ You are not allowed to view attachments ] , and is much better than Google Maps for this type of analysis.

Using Google Earth Pro to find a reference mark north of the station works well when the available imagery is at a sufficient resolution, for example:
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As Google's global collection of high resolution aerial imagery grows, being limited to 2' NAIP imagery (in the U.S.) will become forgotten, but for now, that's all that may be available in certain rural regions. Below is a comparison of 2' NAIP imagery alongside of 6" ortho imagery from MEGIS.
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Offline kbellis

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Re: Determining True North
« Reply #38 on: December 17, 2018, 10:35:24 AM »
:shock:    I think I'll just keep using the North Star.
Here's another wrench in the mix...I use magnetic north. ;)

Compass and Polaris will be in agreement as to north only along the line of zero declination; just keep the wrench and other ferrous objects away from the compass ;)

Offline kbellis

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Re: Determining True North
« Reply #39 on: December 17, 2018, 12:16:56 PM »
If you have a handheld GPS, especially one with waypoint averaging, you can use it to get a good approximation of true north from a given reference point.

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You may want to use another method to evaluate how good your Oregon, or any other single frequency handheld GPS device, like your phone, fitbit, etc., such as what I've laid out in the OP video, or what SLOweather mentioned (if you've good aerial imagery). In this quick example shown above, I stood close to the previously calculated 17wx ref waypoint that was uploaded to the Oregon 550. For those unfamiliar with the display, the triangle represents the user's current position.

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Your Oregon can be configured to display a user grid which will provide northings and eastings to the nearest 1 foot, such as it can. If a more precise device was used, a side discussion about convergence angles might come up, but at the likely short distance between marks, it would still be a moot point. Regardless, you might find using a user grid more convenient than calculating the linear distance from geodetic positions.

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Also, once you've logged your waypoint (or averaged waypoint), your Oregon can project a new point along any bearing; e.g., 0 (true), and distance.

Offline CW2274

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Re: Determining True North
« Reply #40 on: December 17, 2018, 02:23:28 PM »
:shock:    I think I'll just keep using the North Star.
Here's another wrench in the mix...I use magnetic north. ;)
just keep the wrench and other ferrous objects away from the compass ;)
Didn't use a compass..merely aligned the vane to true north (established by Polaris which is conveniently aligned with a Saguaro cactus in the yard and the anny pole to avoid parallax) then dialed in the declination through the console.

Offline kbellis

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Re: Determining True North
« Reply #41 on: December 24, 2018, 10:52:17 AM »
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Waiting for first coat of "Hammered" paint to dry - very industrial look!

Merry Christmas to you all!

Offline DaleReid

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Re: Determining True North
« Reply #42 on: December 24, 2018, 12:13:08 PM »
How in the world???

Beautiful execution.  What did you use for the letters?  Metal or wood?
ECWx.info
&
ECWx.info/t/index.php

Offline kbellis

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Re: Determining True North
« Reply #43 on: December 24, 2018, 12:43:11 PM »
Thanks Dale.

The letters and the fins are cut from some scrap 1 x 4 PVC trim. This stuff works like clear pine without grain and is easily welded with PVC solvent; ie., Weld-On 2007, (and regular PVC pipe cement), and takes paint beautifully.

Full scale drawings of the 3" high letters and 2.5" fins are attached... oops, now they're attached  :oops:. The center 2.5" high hub is Schedule 40 PVC 2" pipe. The fins are drilled and tapped (#10 x 24) for the directionals' threaded rods. The center hub is drilled and tapped (#10 x 24) for the stainless 1/2" set screws that will hold the directional in place on the mast. The letters are all through drilled 13/64".

And of course, I had to Photoshop out the wire holding the assembly in my makeshift spray booth ;)


« Last Edit: December 25, 2018, 12:30:27 AM by kbellis »

Offline kbellis

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Re: Determining True North
« Reply #44 on: January 12, 2019, 01:54:54 PM »
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Taken from the CWOP Guide, v1.0 20050308, D. Helms.


All very interesting...
but the question remains, how accurate do you need to be?