Discussion: Life after Ivar

RMOC used to hire Ivar Helgesen to create our basemaps, but he retired last year.

Has anyone located a digital photogrammetrist who can create orienteering basemaps "the old fashioned way" using aerials / stereo pairs, etc.? Or is LiDAR the only way to go these days?

(I don't fully understand the whole process, so I hope I'm using close enough terminology to get my question across...)

Your question is somewhat akin to asking for a mechanical typewriter. I guess there may still be old photos sitting around, but my impression is that no airplanes will go up anymore to take stereo pairs—am I wrong?

Local (Australia) experience is that an operating photogrammetry machine has a value on the open market somewhat less than the scrap metal value less transport costs. I have heard of two people trying to get rid of them and having no takers other than scrap.

One of the local (again, Aust) survey companies will still do stereo pairs if asked, but they sounded a bit surprised that anyone would want them. I get the impression it's the same theory as the photogrammetry machines - they have the gear, and until it breaks they're happy to be paid to use it, but once it's gone they won't replace it.

Brooke - are you looking for someone to process existing photos, or generate data from scratch for a new area?

Ivar retired in part because he was the right age to be done, and in part because his job had become obsolete. Note that he didn't train a protege or sell his stereoplotter, he burned it. LiDAR is all advantages with no downsides.

There IS a downside. LIDAR-derived contours often show shapes that are not detectable on the ground. They need to be removed for orienteering use. I think that photogrammetrists often did this job for us.

OMG, you mean fieldchecking is still necessary?

(BTW, the Helgesen brothers have been my mapping heroes for 35+ years!)

There are at least two keys to using Lidar data for a base map:

a) Generate twice as dense contours as what you'll need for the final map. This makes it much easier to see if a given curve detail is significant enough to deserve a place on the final map.

b) Generate a slope image to show local inclination.

As gruver notes a purely mathematical set of contours will often result in a lot of noise in relatively flat areas.

What we really want for orienteering is to tweak the ideal contours so that they follow locations where the slope angle is changing! This way they will show the edge of terraces.

When you have raw Lidar (LAS/LAZ) data available the real fun starts with vegetation classification: I have had pretty good results from an iterative process where I start with a default set of classes, then go out and survey some areas:

During this process I determine benchmark spots, i.e. locations that should be mapped as light/normal/dark green, white, yellow, green stripes etc. and then I use these benchmarks on the rest of the terrain, picking the closest match to the benchmark spots.

Any obvious errors in this process is just added to the benchmark list before re-processing.

Pat Blashill may be the only one left...
http://www.stirlingsurveys.co.uk/orienteer.html
(not much LIDAR in Scotland yet - "my impression is that no airplanes will go up to take laser images —am I wrong"? )

The reason I asked is that Colorado doesn't seem to have extensive existing LiDAR coverage like some other states, and we've heard (third-hand) that contracting a custom LiDAR survey (for creation of a new map) is very expensive (compared to flying for aerial photos).

Thanks for the link, Graeme.

Agreed, extra shapes not a problem, but a luxury.

However I strongly disagree with the notion that "LiDAR is all advantages with no downsides"
Yes it is the future, and yes it is superior in some situations, but the situations involve very many factors, such as the terrain, available lidar data, cost of data, the skill of the data manager, the terrain, the available photos, and the terrain, and did I mention the terrain/vegetation characteristics.

In general lidar contours are the main advantage, but not always better. (And yes, get at least double and up to 5x the final interval if graphically feasible).
The main downside is the shortage of line and point features.

There are still a couple of active photogrammetrists. I can't recite them now, but Ivar H mentioned a couple familiar names to me. One of the typical jobs they still do is to add point and line feature to lidar contours.

I can easily believe that photogrammetry may still be the superior solution in Rocky Mountain terrain.

One downside to LIDAR is its availability. There is none in Yukon yet. We are presently getting one base map done by Stirling; another by a Swede whose name I can't recall, but can track down if necessary.

Terje, do you have a writeup of what you are doing -- sounds very interesting. I think I saw some thread from Martin's lastools mailing list but it did not give much detail.

I guess I should say that LiDAR is working toward no downsides. (And note that I haven't personally done any mapping using a LiDAR base.) From what I've seen, line and point features and vegetation are obtainable with proper processing. I've gotten the sense that eddie has done some pretty clever things with his enhanced product, and I've also seen some nice stuff out of West Point. Using plain vanilla LiDAR is apt to be no better than using a plain vanilla engineering base. And yes, availability of data is certainly a factor, although that's a resource that will continue to grow. Custom LiDAR flights aren't necessarily unaffordable, I know of clubs that have done it, just as clubs sometimes used to have custom stereo pairs flown.

Seems to be no reason that a lidar flight would be more or less expensive than stereo pair-taking flight. Either one is pilot's time and fuel. Both involve comparable lines of flight, no?

The difference may be in amortization costs of the equipment. Cameras may already be paid for, and somebody could conceivably be trying to squeeze a little more value out of them. But cameras also have recurring costs (film and processing). Unless there are digital cameras available for this purpose -- I have no idea. But photos may have an advantage if they have already been taken and are on the shelf.

In late 2012 Dartmouth was trying to arrange for some lidar and the prices ranged from about $1150/sq mi to about $2800/sq mi depending on how much was going to be done. I don't know what the actual costs were but this is just to provide a ball park number. The lidar was at 4 or 5 points/sq meter and the company that provided the quote was from Ohio so that's a radius that covers most of the US east of the Mississippi.

An advantage of Lidar is in areas of thick evergreen such as the pine forest of CT. Even the rough form from the state that is publicly available is better than the blanks provided from the stereo analysis.

We are getting the last "old-skool" basemap done by Stirling - I understand they are disassembling their stereo plotter at the end of the month when they finish ours.

Interesting note - when go ordered the diapositives for our map, the company had to find someone in Canada who still had the film, and when we got it, they said that is the last of the film, and after this, there are no more diaps being done in western Canada. All of the photos are now being flown digital. So, it is the end of an age.

@upnorthguy - the Swede recommended to us by Ivar is P-O Derebrant - drb-kartografi at telia dot com

If anyone in North America is interested in doing any photogrammetry themselves, by the way, the last I knew, Pat Dunlavey still had a stereoplotter taking up space in his office and would be happy to have someone haul it away. (He may have junked it in the meantime, though.)

Survey Graphics in Perth offer commercial photogrammetry and Lidar worldwide, acquisition and analysis.

An area with lidar issues -- http://www.attackpoint.org/discussionthread.jsp/me...

Might have had photogrammetry issues as well?

@guskov:

I definitely intend to write an article about the Lidar processing I am doing, the only problem is that I am still modifying my code more or less every day, and I would like a somewhat more stable basis for the article.

All the code is pure Perl (i.e. just like Mr. RouteGadget), but since I call various lastools binaries for things like converting .laz files to .txt format and piping the result into my code it needs a Windows platform.

The steps I use today is

a) Contour lines, including extra help lines, depressions, dot knolls, fall line markers and negative contours.

b) DEM (in ASC format, easy to import and relatively compact)

c) Slope image with some extra emphasis on smaller slope angles, i.e. I use the 0.7th power instead of a linear mapping.

After generating the slope angles I also specialize them into B/W cliff images, with cutoffs based on the angles that corresponds to 1,2,3 m altitude change in 1 m horizontal distance. The main problem with this today is that I tend to get missing ground points at the top of cliff faces, I've had the same issue both with lastools' lasground and with mcclidar, the basic Norwegian LAS file ground classification is just about equivalent.

d) Vegetation classification: I use lasheight (also from lastools) to classify vegetation points into classes that are relevant to orienteering:

Low (class 3): 30 cm to 1.2 m. This is low brush which can impact runnability but not the visibility so it will be mapped with green stripes if sufficiently dense.

Medium (class 4): 1.2 to 4 m. This is the kind of vegetation that gives various levels of green on the map.

High (class 5): 4+ m. Classic white forest here in Scandinavia.

I use the relative densities of points in the Ground/Low/Medium/High to determine a probable vegetation class. In order to get a statistically sufficient number of points I've found that I need to sample a circle with a diameter of about 10 m which I centerweight. This is the raw classification for each 2x2m spot on the map.

The idea for the next step is one I've borrowed from Jarrko: A majority vote among all the classifications around each spot in order to reduce the amount of noise and make the result much more useful. (The majority vote is also center-biased via a set of sampling weights.)

The final step here in Norway is a SOSI to DXF converter: SOSI is the Norwegian Geo coding standard, since it uses UTM (usually in cm) for coordinates it is relatively easy to convert it to DXF with 1m floating point UTM coordinates.

Here is a small comparison:

This summer I ran a social event on a small island south of Fredrikstad:

http://tmsw.no/qr/show_map.php?user=terjem&map...

Here is the north end of the same island after the automated process I outlined above:

http://tmsw.no/o/rossholmen_sample.jpg

The public path data is obviously pretty bad, but all the cabin outlines are pretty exact.

I use half the normal contour width for those extra help lines (1.25 m), this makes it easier to read the map!