Projecting A Webpoint

[motoed]

On the eTrex, there is a feature called "Waypoint Projection". I didn't quite follow what the manual was trying to tell me, Can someone explain a situation or two where you would use this feature for GeoCaching?

 

- Ed

[+GSVNoFixedAbode]

Yep, I've set up a multi that uses projections: Woodhaugh Wanderings. Each point gets the cacher to project to the next point with a bearing and distance. Apart from an original typo - quickly corrected - it seems to have worked ok.

[+=BB=]

For a more direct explanation:

 

The "project waypoint" feature can be accessed by:

 

find waypoint > nearest > select {waypoint name} > text box (beside the X) > project waypoint

 

This feature allows you to place a waypoint a certain distance + bearing away from whatever waypoint you select.

 

Example: you have a waypoint called "start" and you want to project a waypoint called "finish" 800 meters away from "start" at a bearing of 270 degrees. You select: find waypoint > by name > enter in "start" > text box > project waypoint > enter in name "finish" > enter in distance "0000.80 km" > enter in bearing "270" degrees > ok

 

This will create a new waypoint named "finish" with whatever coordinates that is 800m away from "start" at an angle of 270 degrees.

 

Make sense?

[+DBleess]

In the very simplest terms, it lets you set a new waypoint based on another known waypoint. Say you have a benchmark in the gps as a waypoint. You can set a new waypoint due east (bearing 090) at a distance of your choosing, say exactly 1 mile.

 

The gps will calculate the coordinates of that new waypoint and assign them automatically.

 

Does that help?

[motoed]

I think I understand what you guys are saying, But I'm wondering why someone would "practically" want to use that feature.

 

(I just got a Magellan Explorist 100 and I don't think I'm able to do this... Does anyone know if this is typically a Garmin Feature?)

 

- Ed

[+DBleess]

Maybe surveying? Set a waypoint on a benchmark location, then set a bearing and distance to a lot corner, then describe the sides in bearings and lengths.

 

You could describe a mile square or a farm field, or a dragstrip length, or anything with known angles and lengths from a starting point.

 

I've seen words and pictures plowed into farm fields, this would be a good way to do that too. Set angles and segment lengths and plot the waypoints that way.

 

There have been caches that I have found that use it just for giggles to be different.

 

All I can tell you is that the feature is on both my Garmins. Dunno about other brands.

[+embra]

(I just got a Magellan Explorist 100 and I don't think I'm able to do this... Does anyone know if this is typically a Garmin Feature?)

You can do this on SporTraks and Meridians, but I don't know how closely the Explorist firmware follows them. On the Meridian you hit Menu/Projection from the Position screen.

[+Olar]

Remember to specify in your cache description whether your projected compass bearing is Magnetic north or True north. Depending on your location and the projected distance there can be quite a difference. As an example, projecting 1000 metres and having a magnetic declination in your area of 10.5° can mean a difference of approximately 180 metres between the resulting points.

So when hunting a cache that uses waypoint projection make sure your GPSr is set at the North reference used by the hider.

 

Cheers, Olar

[motoed]

I thought I'd share in case anyone is interested.

 

(I have heard rumors of new Magellan's coming out this fall. I have a suspicion that they will be based on the Explorist "body" The backside of the plastic case, has a "die-cut" line in it for what could possibly be a data port, but it's not punched out on the Explorists... Sounds like future planning to me!)

 

But, projecting is VERY simple.

 

You go to the map view (where you see your tracks and point) and move the joystick. At the bottom it tells you, Cursor Mode. and gives a bearing and distance display. So you can visually see on the map in relation to your current position as well as the bearing and distance display. Pretty cool.

 

- Ed

[gm100guy]

I have used this feature when I don't have a topo map of an area but the map has a scale on it. I know I am at the parking lot with my gps and can mark that as a waypoint. I then can set my map to north and use a ruler to measure a distance and put that in the gps and get a waypoint for a trail intesection or what ever I wanted off the map.

 

It is easier to bring a topo though and just input the utm numbers.

 

[+=BB=]

I thought I'd share in case anyone is interested.

 

(I have heard rumors of new Magellan's coming out this fall. I have a suspicion that they will be based on the Explorist "body" The backside of the plastic case, has a "die-cut" line in it for what could possibly be a data port, but it's not punched out on the Explorists... Sounds like future planning to me!)

 

But, projecting is VERY simple.

 

You go to the map view (where you see your tracks and point) and move the joystick. At the bottom it tells you, Cursor Mode. and gives a bearing and distance display. So you can visually see on the map in relation to your current position as well as the bearing and distance display. Pretty cool.

 

- Ed

Using your method is also VERY prone to errors.

 

Once you start doing the intermediate to advanced caches where precise projections are required, you will want to follow the method I listed above.

[motoed]

Using your method is also VERY prone to errors.

 

Once you start doing the intermediate to advanced caches where precise projections are required, you will want to follow the method I listed above.

I'm not suggesting you use it as a visual. You still have a "bearing" and a distance reading at the bottom of the screen when you are moving your cursor. So you can accurately see how far and which way you are "marking" your point from present position.

 

I was just saying that it seemed nice since it gave you both a visual and a numerical projection.

 

(also, zooming in allows you to fine tune the amount that the cursor moves so you can make finite adjustments.)

[+=BB=]

It is true, zooming in can help you become more accurate however the entire procedure is dodgy at best.

 

You really should learn how to project a waypoint properly! It uses a set of mathematical formulae to project an extremely accurate waypoint.

 

Once you start doing more advanced caches (ones that require in-the-field expertise) you will see why I suggest you use the waypoint projection method as opposed to the "pan+scan" method.

[+EScout]

There are some good replies to this topic. Two of my caches use projections (and you might have to use meters and mils.)

As for uses, one of my other hobbies has an annual event where the rules for the club are that all activities be within a 1,000 foot diameter circle. We have used a GPSr to lay out the boundaries.

Once you mark the projection, I recommend using the route function. When you enter waypoints in a route, you can instantly see the bearing and distance.

[+=BB=]

(and you might have to use meters and mils.)

 

That's highly ironic - you managed to name my second cache placement.

 

Meters and Mils - Ottawa, ON, Canada Cache

 

Good point about using the "route" feature - it can help you if you need to mark a waypoint at the intersection of two lines. Example:

 

You are given two waypoints (WP1 and WP2) and you are given a bearing (in MILS) from WP1 to the cache and from WP2 to the cache but no distances in either case. How do you solve this?

 

Answer: Project a new waypoint fromWP1 at a distance of whatever you feel is adequate (I use 10km) at the same bearing from WP1 to the cache and call it WP1B. Do the same fromWP2 using the bearing for WP2 to the cache and call it WP2B. Now that you have 4 waypoints, make a route from WP1 -> WP1B -> WP2B -> WP2 and then check the "map view" of your GPSr. Mark a new waypoint using the "pan+scan" method at the intersection of the two lines. Done!

[+EScout]

=BB=:

I checked out your cache page. Very good description of mils and a good cache to exercise your GPSr. I like the crossing waypoint legs you describe. This works well in my Legend, buy my Meridian does not have this feature.

 

I have used a triangulation exercise, which requires no compass, map, or mapping GPSr, in my cache: Shoreline Triangle

Each of 3 waypoints gives a bearing to the cache. Enter the waypoints and walk from one of them along the bearing, while matching up the other 2 reciprical bearings in the "nearest waypoints" page on your GPSr. I used mils and one finder commented on the accuracy.

Edited August 13, 2004 by EScout