aletheuo
03-10-2009, 01:02 PM
I'd like to explain how I estimate ranges to about +-10%. It all started with an article on Chuck Hawks site Rangefinding in the Wild by Henri Montandon. http://www.chuckhawks.com/rangefinding_wild.htm I suggest you read that article first. It uses a method to estimate ranges in feet - not much use for a hunter. Below I describe a method to estimate ranges in yards. It is the same method except that I create my own unique ratio in the "field."
If you read that article you discover that you need to measure the width of your thumb and the length from your eyeball to your extended arm/thumb. Then you calculate a ratio to use to estimate distances. But for me, when the rubber hit the road I couldn't make it work. Here's what I did to make it work for me - maybe it will help you as well.
Discover your own ratio using Google Earth and an object of known height.
Out my front window I can see a dumpster up the road. I know from experience that dumpsters are about 5 feet high in my area. I then went to google earth and measured the distance from my front window to the dumpster using the ruler tool. You can be quite accurate, too. Now just take the formula and work backwards to determine your own ratio. If the dumpster is 1/3 thumb high then I take the 5 foot term and multiply by the reciprocal (3) to give me 15. ie/ My thumb measures 15 feet high at that distance. (if you are lost, there are real-world examples below)
Now, if the distance you found in google earth is 180 yards (as it is to the dumpster in my case) then you can find your ratio number by doing 180yards/15feet high = 12.
Everyone will have a different ratio. But here are two examples how I used this and my buddies were amazed. A note here is that my method gives distances in yards rather than feet as shown in the Montandon article.
Real World Example 1: Gate down the road is 6 feet high from experience. I hold my thumb out and find that 6 gates can fit on the widest part of my thumb. (I use where the white ring meets the edge)
6feet * 6gates * 12(my ratio)= 432 yards
To check my estimate I used my GPS - got 410 yards. Another check in google earth gave 420 yards. Pretty good range estimation IMHO.
Real World Example 2: Park kiosk is down the trail. I know that I could just touch the top of this - must be 8 feet high. Ok, stick out the thumb - my thumb is about 1.2x the size of the kiosk. ie/ it just covers the kiosk and a bit more
8feet*1.2*12=115 yards
again, pretty slight margin of error because my gps gave me 110 yards.
Hunting Example 1: Elk is 5 feet high at the withers. You see one across on a slide and hold out your thumb and you find that he is 1/4 thumb.
5feet*4*12=240 yards - no problem, in the mpbr of my 270. Shoot away.
Hunting Example 2: Deer is 4 feet at the shoulder. Hold out the thumb. 1/7 thumb.
4feet*7*12=336 yards. - ok, out of MPBR of my rifle. Stalk closer or hold over.
Let me know what you think. Does it work for you like it has for me? Give it a try and I'd love your feedback. You do need to be pretty good with numbers in your head. My only errors in estimation over 10% have been due to bad math. It's, in fact, a digital rangefinder because a digit is a finger.
If you read that article you discover that you need to measure the width of your thumb and the length from your eyeball to your extended arm/thumb. Then you calculate a ratio to use to estimate distances. But for me, when the rubber hit the road I couldn't make it work. Here's what I did to make it work for me - maybe it will help you as well.
Discover your own ratio using Google Earth and an object of known height.
Out my front window I can see a dumpster up the road. I know from experience that dumpsters are about 5 feet high in my area. I then went to google earth and measured the distance from my front window to the dumpster using the ruler tool. You can be quite accurate, too. Now just take the formula and work backwards to determine your own ratio. If the dumpster is 1/3 thumb high then I take the 5 foot term and multiply by the reciprocal (3) to give me 15. ie/ My thumb measures 15 feet high at that distance. (if you are lost, there are real-world examples below)
Now, if the distance you found in google earth is 180 yards (as it is to the dumpster in my case) then you can find your ratio number by doing 180yards/15feet high = 12.
Everyone will have a different ratio. But here are two examples how I used this and my buddies were amazed. A note here is that my method gives distances in yards rather than feet as shown in the Montandon article.
Real World Example 1: Gate down the road is 6 feet high from experience. I hold my thumb out and find that 6 gates can fit on the widest part of my thumb. (I use where the white ring meets the edge)
6feet * 6gates * 12(my ratio)= 432 yards
To check my estimate I used my GPS - got 410 yards. Another check in google earth gave 420 yards. Pretty good range estimation IMHO.
Real World Example 2: Park kiosk is down the trail. I know that I could just touch the top of this - must be 8 feet high. Ok, stick out the thumb - my thumb is about 1.2x the size of the kiosk. ie/ it just covers the kiosk and a bit more
8feet*1.2*12=115 yards
again, pretty slight margin of error because my gps gave me 110 yards.
Hunting Example 1: Elk is 5 feet high at the withers. You see one across on a slide and hold out your thumb and you find that he is 1/4 thumb.
5feet*4*12=240 yards - no problem, in the mpbr of my 270. Shoot away.
Hunting Example 2: Deer is 4 feet at the shoulder. Hold out the thumb. 1/7 thumb.
4feet*7*12=336 yards. - ok, out of MPBR of my rifle. Stalk closer or hold over.
Let me know what you think. Does it work for you like it has for me? Give it a try and I'd love your feedback. You do need to be pretty good with numbers in your head. My only errors in estimation over 10% have been due to bad math. It's, in fact, a digital rangefinder because a digit is a finger.