+pictom Posted February 9, 2011 Share Posted February 9, 2011 How do I estimate the height of an object (a tree) using my GPS. I am sure I have seen this information before and I am sure I even tried it out. Now I need to do it and don't recall anything about how to do it or where I found the information. I have searched "Estimating Height" on the boards and they state you can not do it, but those messages are several years old and the technology has changed enough to make this possible. All I seem to recall is you point the antenna at the tip of the object. Thanks in advance for leading me in the right direction on this! Quote Link to comment
+dfx Posted February 9, 2011 Share Posted February 9, 2011 You climb the tree to the top, drop the GPS and take the time it takes for it to hit the ground. h = 1/2 g t2 Quote Link to comment
NordicMan Posted February 9, 2011 Share Posted February 9, 2011 (edited) I doubt you could estimate the height of a tree (for example) using a handheld GPSr at least not with any amount of accuracy. Maybe a monster Redwood but not a lowly apple tree Does your attempt mean you are going to climb to the top of the tree & compare the displayed altitude & subtract from ground level altitude? On a fancier GPSr you can technically either use the GPS altitude or the barometric pressure altitude, which would probably be more accurate. Edit: Another method, if the area was level ground, is to step 100 feet away from the base of the tree (according to the GPS), determine the angle from the ground to the tree top, and use good'ole trigonometry to math out your solution. ..Or do what dfx suggests Edited February 9, 2011 by NordicMan Quote Link to comment
+dfx Posted February 9, 2011 Share Posted February 9, 2011 (edited) Only thing I can think of is geometry. Use the GPS to measure the distance between the tree and any random spot, and then take the angle from that spot to the top of the tree (against the level ground). I wouldn't know how to use the GPS to measure the angle though. Errr nevermind, has already been mentioned Edited February 9, 2011 by dfx Quote Link to comment
+janandsteve Posted February 9, 2011 Share Posted February 9, 2011 How do I estimate the height of an object (a tree) using my GPS. I am sure I have seen this information before and I am sure I even tried it out. Now I need to do it and don't recall anything about how to do it or where I found the information. I have searched "Estimating Height" on the boards and they state you can not do it, but those messages are several years old and the technology has changed enough to make this possible. All I seem to recall is you point the antenna at the tip of the object. Thanks in advance for leading me in the right direction on this! A google of 'measure height with gps'....... revealed this....... http://www.fig.net/pub/athens/papers/ts07/ts07_6_svabensky_weigel.pdf Hope that helps..... Quote Link to comment
+pictom Posted February 10, 2011 Author Share Posted February 10, 2011 Thanks everyone. I was sure this was a built in feature. Now I do not know what it was I was doing when I was pointing my antenna at an object. I don't think it was projecting a waypoint but maybe it was. Hopefully I'll have time to play around with all the settings soon. Thanks again! Quote Link to comment
+Walts Hunting Posted February 10, 2011 Share Posted February 10, 2011 You climb the tree to the top, drop the GPS and take the time it takes for it to hit the ground. h = 1/2 g t2 While the formula is correct and will work for whatever g is defined (earth is 32 feet squared per second but other planets would be different) it is easier to simply for earth as 16 multiplied by time in seconds squared. I actually used this recently to setup a pulley system for a CITO and wanted to know how high the bridge. Didn't use my GPS to drop but a rock and timed it. Quote Link to comment
+dfx Posted February 10, 2011 Share Posted February 10, 2011 Didn't use my GPS to drop but a rock and timed it. You didn't do it right then! Quote Link to comment
+The Kamikaze Clan Posted February 10, 2011 Share Posted February 10, 2011 My Nautiz X7 GIS PDA can measure angles. I have used it a few times to estimate height. Quote Link to comment
+Capt. Bob Posted February 10, 2011 Share Posted February 10, 2011 Place the gps on the ground, standing on end. Measure the length of it's shadow. Now measure the length of the tree's shadow. The ratio will be the same. Tree Height = (GPS Height X Tree Shadow) / GPS Shadow Quote Link to comment
+julianh Posted February 12, 2011 Share Posted February 12, 2011 Measure the length of your GPS; climb the tree, marking off GPS lengths as you go; count how many GPS's tall the tree is ... Voilà!!!! or ... Find a forest ranger or lumberjack who knows how tall the tree is; tell him you will give him your GPS if he will tell you how tall the tree is. Hope this helps! Quote Link to comment
+myotis Posted February 12, 2011 Share Posted February 12, 2011 Only thing I can think of is geometry. Use the GPS to measure the distance between the tree and any random spot, and then take the angle from that spot to the top of the tree If you have a Wherigo capable GPS, you can get the AstroToolbox. It will give you the altitude of the sun. With the sun altitude and using the GPS to measure the length of the shadow, you can use math to figure out the height. Height = tangent of Sun’s altitude X shadow of the tree. Maybe someone could write a Wherigo app to do the math. If you have a camera in your GPS, have someone of known hieght stand next to the tree and take their picture. You should be able to use the picture to figure out how many times taller the tree is than them and do the math. Quote Link to comment
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