gps grids on maps

Submitted: Sunday, Mar 13, 2005 at 19:56
ThreadID: 21193 Views:1573 Replies:9 FollowUps:1
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hi guys, might be a stupid question to some but, i have the set of desert treck maps from hema and i am going on a trip soon i have a gps but i was wondering how to read the gps grid on the maps..........
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Reply By: 80scruiser - Sunday, Mar 13, 2005 at 20:31

Sunday, Mar 13, 2005 at 20:31
Go to your nearest Boots store. They have a great little book on GPS operation.
Answers all questions. Apart from that 4x4 monthly had an article a couple of years ago which was simple and to the point. Apart from that 4WD monthly brought out a mag called "Australia by 4wd" recently and it has Navigation Essentials spread through out. Good, accurate and to the point.
AnswerID: 102271

Reply By: Mike-TS - Sunday, Mar 13, 2005 at 22:49

Sunday, Mar 13, 2005 at 22:49
They should have lat-long or some other grid datum on the maps? You identify your point of interest then scale off x and y grid and input into your GPS.

Easier if your have oziexplorer or similar product as scaling can be quite a distance off on the actual ground - 100s of metres is not untypically!
AnswerID: 102300

Reply By: The Explorer - Sunday, Mar 13, 2005 at 22:52

Sunday, Mar 13, 2005 at 22:52
Hello – there is a bit of info on the HEMA maps for GPS users…it says – “For best results and ease of use set the datum to WGS84 and set coordinate style to degrees, minutes and seconds (DD MM SS) eg 25° 08’ 31” Position accuracy is limited by the scale of the maps” So…basically make sure you set and co-ordinate readout on your GPS to be the same as the map you are using (applies to all maps). As Hema mention, because the maps are such small scale( 1:1,250,000!!) they are not that accurate eg the road is depicted as a line about 400m wide (your GPS should be accurate to ~5m)..but for the average 4wd driver this is not an issue.

To actually plot your position on the map use the co-ords lines and tick marks on the shown on the map. The major lines on the GDT Hema maps are every 30 minutes (eg 129°00’ then 129°30’ the 130°00’ etc ) – you will then see minor subdivision tick marks on the major co-ord lines - these are every 5 minutes (129° 05’00” then 129°10’00” then 129°15’00” then 129°20’00 then 129°25’00 then129°30’00 etc). You will have to guess the seconds yourself keeping in mind that the are 1/60th of a minute i.e. 30 seconds = ½ of a minute subdivision.
Hope this helps - have fun.
Cheers
Greg
I sent one final shout after him to stick to the track, to which he replied “All right,” That was the last ever seen of Gibson - E Giles 23 April 1874

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AnswerID: 102301

Reply By: Member Colin - NSW Bungendore - Sunday, Mar 13, 2005 at 23:09

Sunday, Mar 13, 2005 at 23:09
As has been mentioned - larger scale maps don't have a Grid on them ie. most Hema maps.
Smaller scale maps do have a grid ie 1:250 000 & 1:100 000.
I personally think that Lat & Long are pretty useless as you cant measure this on any map - I would stick with Grids unless you are using larger scale maps.
AnswerID: 102309

Reply By: Crackles - Sunday, Mar 13, 2005 at 23:51

Sunday, Mar 13, 2005 at 23:51
Describing how to read maps in a short paragraph is difficult & 80scruiser's suggestion of getting some books on the subject is probably best.
Briefly though you need to set your GPS up to the same Datum as the map which is WGS84. You then need to set the Projection to Degrees, minutes & seconds so that all the Coordinates on the map correspond to your GPS. (details of how to do this are in your GPS handbook)
Now to read the Hema map.(Other maps will be marked different) The numbers corosponding with every 2nd blue line accoss the top of the map is the Longitude & the ones down the side the Latitude.
Every 2nd blue line is one Degree which is also divided by 12 marks each equal to 5 minutes. There are 60" (seconds) in a minute & 60' (minutes) in a degree.
Now the Coordinates of locations on all maps are always given with the Latitude first followed by the Longitude.
So to practice Grab the North West Sheet. Find Halls Creek in the top right.
Reading down the side its just past the 18 degree line with a bit more than 2 & a half blue marks so would read 18 degrees, (& about) 13 minutes & the seconds would be too hard to split on a 1:1250,000 scale map.
Reading accross the top we have 127 degrees plus 8 marks equaling 40 minutes.
The coordinate then reads 18degrees, 13', 00" / 127degrees 40', 00" This although not completely accurate will get you to within 500m or so of the town.
Have a look at some of the coordinates placed on the map & transpose them accross to the side to get an idea how the grid is divided up.
As previously said it's very hard to describe & I hope I havn't confused you more.
Cheers Craig..............
AnswerID: 102315

Reply By: Member - Chrispy (NSW) - Monday, Mar 14, 2005 at 07:57

Monday, Mar 14, 2005 at 07:57
The best little book that I have found for people new to GPS is from the Department of Lands. It's called "Map Reading Guide for Topographic Maps". Published in 2004 - so it's fully up to date, and only costs $2.75 at your local outdoors centre.70 pages of really good info. It doesn't concentrate on GPS as such, but how to interpret all features of a topo map, which is more important. It does go into using a GPS with them, and in particular how to use UTM coordinates properly. Once you understand the map system properly, the book that comes with your GPS suddenly makes a whole lot of sense.

ISBN 07313 8839 7

AnswerID: 102325

Reply By: Wizard1 - Monday, Mar 14, 2005 at 15:08

Monday, Mar 14, 2005 at 15:08
Join the boy scouts or army and they will teach you how to read maps and use grid systems......

Wizard
Gold Coast

AnswerID: 102371

Follow Up By: damon1 - Monday, Mar 14, 2005 at 20:45

Monday, Mar 14, 2005 at 20:45
Thanks Wizard but that is not really a constructive answer.........
0
FollowupID: 360149

Reply By: Gossy - Monday, Mar 14, 2005 at 17:04

Monday, Mar 14, 2005 at 17:04
11 years in the Army has taught me that Lat Long sucks. Set you GPS to grid and only buy grid maps and you will never look back. Grid maps also have contour lines so even if you lose your way you can orientate your map north on the ground, and figure out the features (spur lines, creek lines etc) around you.
I guess at the end of the day it comes down to personal preference. I tried Lat Long on the birdsville trek recently and hated the lack of information on the map itself. It just didn't feel right going thru creek lines etc and nothing marked on the map to show the feature! I come from the old school of having absolute knowledge of where you are on the map by good map reading. Using technology like a GPS is just a secondary method of locating your position.
AnswerID: 102378

Reply By: damon1 - Monday, Mar 14, 2005 at 20:55

Monday, Mar 14, 2005 at 20:55
thanks guys
AnswerID: 102416

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