Bushwalk Australia

Here's the issue:
I'm very proficient at reading 1:50,000 maps for bushwalking purposes.
I now have a GPS (eTrex 20x)
I want to input a waypoint from the paper topo map into my GPS
The reason I want to do this is that navigation to this point (on an upcoming walk) is tricky by map and compass alone.
Then when I get into the field I can follow the GPS (and map) to that point
However, I'm aware that I cannot input Australian Map Grid Coordinates straight into the Garmin GPS
The solution must be to input the Lat/Long coordinates.
My topographic map does have Lat/Long markings along the side - but there are no grid lines!!
So trying to read a very accurate Lat/Long point is impossible.

Here's my answer:
Take an appropriately graduated ruler and measure the S and E
Then input the numbers from the ruler into the GPS.... done?
I've noticed that Lat/Long rulers are available, but the distance does vary between grid lines with Longitude across the globe obviously.
https://www.maptools.com/lat_lon_tools

Sorry if that's long winded. Am I on the right track here?

I think you need a better map that does have a grid and UTM coordinates.
Then input UTM cordinates.
Does this video help as a how to?
https://www.youtube.com/watch?v=HoBmJbgEmFU

You can add the waypoints in the GPS in Australian Map Grid. Just change the settings in the GPS to Australian map grid. Then add a waypoint and edit the coordinates.

Which GPS do you have?

Change the GPS position format to UTM UPS and the Datum to GDA

tastrax wrote:Change the GPS position format to UTM UPS and the Datum to GDA

That is if the map datum is GDA.
An older map might be AGD66.

Correct, but I suspect most new maps will be GDA.

Unfortunately in South Australia the topo maps have not been updated for many years. The 1:50,000 map of the Flinders Ranges goes back to the 1979. Even the newer strip maps of the Hysen Trail are still only working from those original aerial photographs of the 70's. Attached is a scan of my map. The place of interest is Dead Goat Soak (in green). Getting a AMG coordinates of this point is easy.
I've highlighted the S and E in red and blue. Note how their are NO grid lines stemming from these markings on the side.

Is there something on the map that indicates a datum...like Horizontal Datum Australian Geodetic Datum 1966?

Dead Goat Soak would have a reference like

264700mE and 6546100mN which you can then plug into the GPS

a quick google search also found the lat long in decimal degrees -31.193679809 and 138.531875610

and slotting that into Google earth allowed me to get 31°11'37.25"S and 138°31'54.75"E

You should be able to do something with any of those

Hey you got the drop on me while is was fumbling with the keyboard Phil and our guesses are pretty close to one another.
But here's my contribution anyway.

Looking at the scan - your spot is approximately UTM 54J E264700 N6546150.
By guesstimate using AGD66 as a datum because it is an old pre 1980's map the approximate Lat/Lon is S31 11 41.9 E138 31 50.1 which seems by eye to be somewhere near the spot on the map.
The point of this was to establish which utm zone you are looking at if it isn't written on the map somewhere.

Your approximate coordinate that would be entered in a Garmin GPS is 54 J 264700 6546150.

I strongly recommend that you work out and enter some local (to your home) coordinates into your GPS from a map that has all the required details of UTM zone and Datum and that you can prove to be correct before you try anything that puts you at risk.

There is lots of good GPS info and links on Bushwalk.com that will help. Just search for what you need.

It is very important to have the GPS set to the correct Datum, matching your paper map, when you enter coordinates from your map.
The difference between AGD and GDA is around 200 metres.

I am still surprised that you cant change over the display in your GPS to Aus Geod '66 (If that is the map datum) and just enter the points as normal rather than mucking around with Lat Long

Don't know if this will help but there is some info on setting up a Garmin for old datums here: viewtopic.php?f=21&t=11137

Michael.

Of course - grid zone required! You can also show that on Google Earth as well

If you get your coordinates from Google Earth they will be WGS84. At this point we are assuming your map is AGD66.
Set your GPS datum to WGS84. After the Google Earth coordinates are entered you can switch back to AGD66 and the GPS will adjust all of them to suit your paper map readings.
Remember to switch to WGS84 if you enter more Google Earth coordinates and then back to AGD66 to match your map. As mentioned above assuming the paper map datum is AGD66.

Not on topic I suppose but I thought I would mention that you can scan your map and add to you extrex via this process in case it might be of assistance. This is more useful if you draw your route on the map or add a gpx track. Size is a limitation if I recall correctly.
http://www.garmin.com/us/products/onthetrail/custommaps

A handy tool - http://www.binaryearth.net/AusDatumTool/index.php

No affiliations on my part.