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Mapping

Show Profile  Michael Posted: 15 May 2012, 2:38 PM  
And talking of MTBO, NZOF has adopted the draft NZ MTBO Rules. The significance for mappers is that they embody some conventions for allowing off-track travel. The IOF speci doesn't lay it down. It has an Appendix containing 4 draft possibilities, all of which have flaws. We reckon we have something better, that which was used in Otago. Off-track isn't usually as much fun as riding tracks, but its special significance is where tracks come close together. We get round lots of issues if we can allow hop-across, and the conventions let us show it.

The NZ MTBO mapping conventions are described in rider terms in the rules. Go to the MTBO website www.mapsport.co.nz/mtbo/mtbo.html and into "Resources", and look for "MTBO Rules".

There's also a description in mapper terms. Go to "Resources" and look for "MTBO Mapping". The MTBO Committee welcomes any feedback or questions: michael (dot) wood (at) mapsport.co.nz

Show Profile  Michael Posted: 21 May 2012, 2:32 PM  
Anyone know anything about the SIRF IV chip? Is it on consumer-level GPSs yet, or smartphones? Any other GPS advances here or nearly here? What about devices that can use the satellites that the Russians or the Europeans are putting up?

Show Profile  Dwayne Posted: 21 May 2012, 3:15 PM  
All the latest Garmin watches have SirfStar IV (including the cheapest FR110 - my daughter has one). My old school FR305 has SirfStar III chip. The SirfStar IV is heaps faster to pick up a signal - 30s vs 1:30 is average. The iPhone 4s has GPS and GLONASS (russian) chips built in. My new phone has GPS-A (assisted) which means it uses the cellphone towers to help locate satellites quicker - sometimes within 10 seconds of turning on the GPS. The Europeans only have 2 sattelites up currently I think. Chinese have about half of theirs up, but mainly cover northern hemisphere at the moment

Show Profile  mark Posted: 21 May 2012, 3:16 PM  
The latest Garmin eTrex handhelds use the Russian GLONASS satellites as well as GPS.
I think the Samsung Galaxy S2 uses the SIRF IV.

Show Profile  Michael Posted: 21 May 2012, 4:53 PM  
Thanks. Do these make an appreciable difference to accuracy? I'm quite prepared to wait a minute longer to pick up signal. I'm hardly ever dropping signal even in heavy bush but would like greater consistency and freedom from rogue wanderings.

Show Profile  Dwayne Posted: 22 May 2012, 8:22 AM  
Selwyn Palmer is the one who I would talk to about using GPS for field work etc. But I doubt that he is listening in here.

Show Profile  mark Posted: 22 May 2012, 9:30 AM  
I discovered last night that my Sony phone picks up both GLONASS satellites and GPS and the accuracy is still crap compared to a Garmin GPS only handheld.

Show Profile  Michael Posted: 26 May 2012, 5:39 PM  
The 1:10,000 symbol sizes are a straight 150% enlargement over the 1:15,000 ones. Except that (in the old days) the dot density for shades of eg green didn't change, this is explicitly stated in the spec. I guess it was supposed to be so fine you couldn't see it.

Now I'm wondering about the stripe pattern for undergrowth. It's acknowledged to be an awful symbol in that it's hard to see other detail though it, and it gets pretty clunky at 1:10,000. I wonder what mappers think about using the 1:15,000 dimensions for these on a 1:10,000 map (407 and 409). Another clunky one is the distinctive vegetation boundary 416, what about that?

My current project is actually 1:7500 (using the 10,000 symbol sizes).

Show Profile  Kenny Posted: 3 June 2012, 11:40 PM  
Michael, re SIRF in GPSrs, phones. On the home page of OZ Mappers Corner for OCAD Users site (http://www.homepages.ihug.com.au/~cartography/links.htm) there is a link to a relevant item I recently sent in. It expands a little on the info already given. Geoff Peck's original comment may be of interest also.

Accuracy of GPSrs down under is improved if WAAS is turned off. See http://www.gpsoz.com.au/WAAS.htm

btw I abandoned plans to test my Android against my SIRFStar IV Garmin eTrex or 402 when I realised my year old Android has a SIRFStar III chip. No contest!


Show Profile  Kenny Posted: 3 June 2012, 11:42 PM  
oops, that should have been Garmin 205 not 402.

Show Profile  Michael Posted: 6 June 2012, 12:47 PM  
A bit more on green stripes. I wonder if that tricky area of boxthorn at Hydrabad (QB long distance) could have used something other than stripes to show that speed there was a bit slower. The full yellow 401 wasn't used at all, if it had been then pale yellow 403 could have sufficed, without needing stripes except for very bad bits. After all, speed between the bushes was quite fast.

I briefly thought about scattered trees 402/404, but the mottled effect of those is just as problematic as stripes. Other thoughts?

Show Profile  mcroxford Posted: 6 June 2012, 5:31 PM  
Is anyone else following the Facebook thread of Routegadget at the moment? We have sourced a lot of Lidar data recently from our local Council and following his process with interest.

Show Profile  Selwyn Posted: 7 June 2012, 5:13 PM  
Every few months I look at stuff on Maptalk. I see Dwayne dropped my name in it.
When I upgraded from 60CSx to 62s (SiRFstarIV chip) there was a noticeable improvement in accuracy, and especially in speed of acquiring satellites. In forest I always plug in a Gilsson antenna and tape it to my shoulder which makes a significant difference under trees. I think Michael puts his antenna on his hat.
My 62s lost its ability to recalibrate the compass while I was cycling in the States. By the time I got home it was out of warranty. I had a prolonged discussion with Garmin Australia about NZ Consumer law. They eventually replaced it. It still would have been fine for orienteering mapping as I used a real compass for that.
But while I was waiting I bought a Montana 650t which is possibly a slight improvement on reception, but it's really cumbersome to take fieldworking, so the Montana is great for geocaching and cycle touring, but I've gone back to the 62s for mapping.

Show Profile  Selwyn Posted: 7 June 2012, 5:40 PM  
Re: Base map contours.
For several years in Auckland we have had available Lidar generated contours from the Auckland Council, 1m in rural areas and 0.5m urban.
Initially we had to pay for it and it came as georeferenced tiff. Then it became downloadable in small areas from their website as dxf for contours and jpg for photos. And from OCAD10 it could be slotted straight into the map as it came with a georeferencing file.
The Woodhill contours provided mixed results; sometimes showing no detail where there were 6m high ridges, but perfect in other places, so I mapped all the the unshown features using the GPS.
From last year Council started supplying the files free.
Last week I got through to a clued up person in the GIS department who sent my the base data, that's the XYZ (Lat. Long. Elevation)data that was recorded by aircraft. It could be supplied in all sorts of formats, but I took asc, dxf and text for an area of Woodhill of about 10 sq km. OCAD11 Beta (or my computer) couldn't cope with the dxf file which was millions of spot points with the XYZ in text - all georeferenced on the OCAD map. Used the DEM function in OCAD11 (should work in OCAD10 Standard as well)to load in the text file, and also tried the .asc file which was much larger. In both cases my OCAD map now showed elevation as well as NZTM coordinates for where the cursor was located.
The rural samples are supposed to be 5m apart and to 0.1m accuracy. But on the map moving the cursor even 2m gave a different elevation to 0.1m accuracy.
Then OCAD 10 and 11 can generate it's own contours using the XYZ data. Had some trouble getting this to happen using OCAD11 Beta, I think because I was initially impatient. The asc



Show Profile  Selwyn Posted: 7 June 2012, 6:02 PM  
Re: Base map contours. continued (I inadvertently posted the message)
The .asc file had nearly 26 million points, OCAD11 supposedly can handle 25 million. But it went ahead and did the processing anyway. I had asked for 1m contours (to compare with the Council contours) and 5m contours. It took 10-12 hours for OCAD to process and create the contours; it's a reasonably good PC with Quad4 processors and fast video card. But the result is many times more detailed than the Council generated contours, even showing little dots in places. Happily, many of those knolls and depressions that I had previously mapped using the GPS were now showing.
I reckon this will make mapping a whole lot easier in the forest.
I have asked the nice friendly GIS Council lady to send me more files to cover Woodhill up to and including Rob and Marquit's house, including an experimental urban tree top elevation file in Monte Cecelia Park near home.
The first generated 1m contour file in OCAD was 51MB which is using polygon format. So I selected the whole lot and used the ..to Bezier function, took about 1 minute, and exactgly the same lines are now 11 MB. I can perhaps break that down into partial maps for quicker convenient use with a specific map area.
Tonight I hope to set OCAD the task of making 2.5m contours for the same area to compare the results.
So for any maps you are making in the Auckland Council area, keep in touch, I can possibly help with this data. No doubt there are other Councils out there that have such data stored away. Auckland could also supply in Shape or LAS formats.
The zipped file download I got from the Council was 141 MB so fast broadband is a good idea.


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