Thread: using GPS as a rangefinder

my brandnew 2nd hand GPS unit arrived today.while having quick glance in users manual (no Im not gay LOL) I spotted a feature I didnt know existed.
if you mark waypoint and move curser on to another place ,it will tell you distance to that other point....
so if Im sitting on ridge/gully/anywhere really and animal is on feature I can spot on map...or another feature is on similar distance or halfway...or double the distance I can dead reckon distance by moving cursor onto that feature and seeing what GPS says.
probably something you lot already knew,but it sure as shite is news to me.
looking forward to learning how to make this thing work...having decent waypoints and trails saved etc

Didn't know but do now thanks

That will give you a ball park distance MD, but won’t be as accurate as a laser rangefinder. Somewhere the gps unit will give you an estimate of the accuracy of it’s position. If this accuracy was say 20 meters, then it means that your actual position will be somewhere in a circle with a radius of 20 meters of the gps position, and the same for the place you move your cursor to.

20 meters would be quite a poor accuracy for a modern gps, but the accuracy is dependent on the number of satellites visible to the gps unit (possibly not many if you are low in a valley) and their relative geometry or position in the sky.

I should have also said that the accuracy is continually changing as the satellites it chooses to use to calculate position also changes.

Can you also use the cursor to set a "navigate to" point? When you shoot said animal and lays in the deep tussock it narrows down the search area.

Having the "snail trail" to follow back is bloody handy for coming back down that ridge line in the dark. Zoom in and it'll show you if you're more than a couple of meters off.

correct..but that 40 mtr of possible error,PLUS my say 20mtrs of error in determining where feature is...gives me 60 mtrs error...my eyetrometer may or may not be that good.
forever and a day my eyetrometer is good enough for 300 yards or less......

Originally Posted by Joe_90

Can you also use the cursor to set a "navigate to" point? When you shoot said animal and lays in the deep tussock it narrows down the search area.

Having the "snail trail" to follow back is bloody handy for coming back down that ridge line in the dark. Zoom in and it'll show you if you're more than a couple of meters off.

yeah you can point n set...tried it in flat field some time back and wasnt very impressed with accuracy...was better off using compass bearing only....BUT YOU COULD use both...eg take compass bearing on compass..... set way point where you stand/shot from and guestimate distance to animal...then when you get over to area,look at where waypoint is if you near enough it should be 180 degrees off your origonal bearing... easy in open country to look back to feature...not so easy if cant still see or make out origonal point...

Sounds like you've been having a good old tinker then
I've learnt from tahr hunting the terrain looks totally different from the other direction...

Yea i use the gps as a range finder & when I have compared it to my old man's range finder the most I was out was 30m that's useing it under 500ms tho lest it gives you a better idea than guessing

As said above it is better than guessing but I got a nikon range finder off the buy and sell here for 200 bucks. Yes it's another thing to carry or lose but it's worth it for accurate measurement. I'd hate to miss a decent stag over not wanting to spend a couple hundred bucks.

I mainly use the distance finding tool to ensure I get back tj camp before too dark

You CAN use GPS or phone (Balistic app with maps etc) as a rangefinder when you are in a low drop zone, ie probably 100-200m. After that the inaccuracies will most likely mean a miss for you.
As previously stated, if your accuracy is +-10m and your pinpoint is +-20m (which is hard to determine exactly unless you have significantly good terrain markers), and you are say 150m range (which you do not know exactly), you have an uncertainty of 150m +-30m, so anything between 120m and 180m.
If you shoot a 180gr 308 projectile, your drop between the 120 and 180m may be roughly 285-123=162mm. Still good enough to hit - maybe just about.
If we do the same calculation for say a distance of 200m (so a range of error between 170m and 230m), your drop will be 478-253=225mm between the two distances. A chance for a miss.
And now we add any angles to it ie down or up and it get a wee bit more complex. The further you go, the worse the error drop gets and the more important range accuracy gets.

So my take on this thing:
For 100m you do not need a rangefinder or GPS. You shoot, you hit - if your rifle is sighted in to 100m or hold a tad under if zeroed to 200m.
For 200m your GPS may be handy but you could also do a shoot and most likely hit if your rifle is zeroed to 200m.
For 300m and over the accuracy will not be enough.

All the above will depend on your zeroing, your caliber and the projectiles you are shooting.

I shoot Rimfire at ~200m and GPS is way, way to inaccurate. the drop difference at even 5m is massive (~90mm per 5m)

A decent range finder is worth its weight.

Range find the animal, take the shot, leave some loo paper up high where you can hopefully spot it, looking back, take a bearing with the GPS or compass as to where the animal was. Then go looking. You have the distant and rough bearing to reverse. Puts me within Cooee of the animal where shot. Better than nothing. Better still get a good Dog.

I've got a cheapie rangefinder off Aliexpress that works fine.
Bought after sitting over a clearing I estimated #~280m. Over the course of the next hour I waxed and waned on the estimation and when a couple of deer came out I settled on 320m and put 2 shots over ones back. Lol

@Micky Duck. Amazing bit of equipment. Be careful with the sight and go, leastways my experience, real bitch to get rid of the straight line that suddenly appears from your position to another. Seems to appear by majic at times. Otherwise really brilliant.

Originally Posted by Joe_90

Can you also use the cursor to set a "navigate to" point? When you shoot said animal and lays in the deep tussock it narrows down the search area.

Having the "snail trail" to follow back is bloody handy for coming back down that ridge line in the dark. Zoom in and it'll show you if you're more than a couple of meters off.

I use the app on my iphone (NZ topo 50) to find shot deer all the time it's an awesome feature.

First you measure the distance using your range finder, then you take a bearing to the deer using your compass, then you use the 'project a way point' feature to enter in both these values to get within 15-20m of the deer.

I believe that most GPS units have this feature also.

Just make sure that your GPS is set to take 'magnetic bearings' not 'true north' bearings and you'll be sweet.

Unfortunately i believe the android version of NZ Topo 50 doesn't have this feature yet.

Originally Posted by Tui4Me

I use the app on my iphone (NZ topo 50) to find shot deer all the time it's an awesome feature.

First you measure the distance using your range finder, then you take a bearing to the deer using your compass, then you use the 'project a way point' feature to enter in both these values to get within 15-20m of the deer.

I believe that most GPS units have this feature also.

Just make sure that your GPS is set to take 'magnetic bearings' not 'true north' bearings and you'll be sweet.

Unfortunately i believe the android version of NZ Topo 50 doesn't have this feature yet.

That's a great tip, thanks for sharing.