Re: [talk-ph] On editing PH coastlines
I have also been doing "coastal cleanup" lately. Main reason being that since I use OSM map tiles for waypoints.ph and since a lot of our destination waypoints are near the coasline (beaches and island destinations are the most popular), I wanted to have good coastline detail on OSM and correct those current "sawtooth" coasts. Most interesting to clean up is the area around west Batangas, especially north Nasugbu which have dozens of mini peninsulas and promontories. They are interesting to look at now (on Osmarender for now as Mapnik may still take time to update the coasts) http://openstreetmap.com/?lat=14.1316&lon=120.6185&zoom=13&layers=0B00FTF I did encounter similar concerns as Maning had too regarding mangroves and wide rivers. I am more particularly concerned if the landsat is actually accurate enough for mapping smaller details such as rivers ... similar problem with Yahoo imagery on Makati as reported earlier on another discussion. Just recently, we took tracks and points on the Mangrove Project of Sariaya. We particularly and specifically navigated the wide river that divides the mangrove area and the tracks were taken with a GPS276C with external antena on the boat and had more than 8 satellites in view (very low position error). Now, when the tracks were superimposed on JOSM against the WMS landsat image, the river was off by as muchg as 50 meters! I just went ahead and used the GPS tracks instead of the landsat image for plotting the river: http://openstreetmap.org/?lat=13.82952&lon=121.46565&zoom=15&layers=B000FTF As what really to follow as "coastline", my opinion is to make existing structures or natural "protrusions" as the coastline. Not knowing what to really follow earlier, I looked at what was done to represent the coastline on the Manila Bay and Malabon area and I see that the coastline was traced along the piers and man-made "land" areas. So, I guess that will do well for showing piers / wharfs / mangroves /very wide beaches / tidal lands. :>) ed On Fri, Apr 10, 2009 at 11:46 AM, Maning Sambale wrote: > Hi, > > Since my etrex GPS died, I have resorted to coastline mapping to > improve previous coastline import. I have completed several islands > already and my next target is Luzon mainland (already completed most of > north-east Luzon up to Ilocos Sur). At first, I thought it should be > easy, just load LANDSAT WMS and your good to go. But really it isn't. > > Because, > > 1) coastline is a fractal problem [1], at varying zoom-levels you get > different details. Using landsat, you need to be at zoom 14-16 to get > the most detail. > > 2) I find it difficult to select, move, and delete nodes of the SRTM > generated coastline. You have to use several keystrokes and > mouse-clicks. What I do instead is delete several coastline ways and > then create a new coastline way. > > Some questions: > > 1) How do we map mangrove [2] areas along coastlines? In the "field" > mangroves are either inland extending to the coast and even beyond > coastline. Do we include mangroves in inter-tidal areas as part of the > coastline? > > 2) Where do coastline and large rivers converge? River deltas [3] is > particularly problematic. > > 3) Sand bars? Siltation areas? Any suggestions on how we map this? > > Me thinks: coastlines will never be complete because we have so much > coastline and the threat of sea-level rise due to climate change > > > > > [1] http://library.thinkquest.org/26242/full/ap/ap4.html > [2] http://en.wikipedia.org/wiki/Mangroves > [3] http://en.wikipedia.org/wiki/River_delta > > -- > cheers, > maning > -- > "Freedom is still the most radical idea of all" -N.Branden > wiki: http://esambale.wikispaces.com/ > blog: http://epsg4253.wordpress.com/ > -- > > > ___ > talk-ph mailing list > talk-ph@openstreetmap.org > http://lists.openstreetmap.org/listinfo/talk-ph > -- website administrator: - www.waypoints.ph - reeflife.eppgarcia.com PADI Divemaster #491048 ___ talk-ph mailing list talk-ph@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ph
[talk-ph] On editing PH coastlines
Hi, Since my etrex GPS died, I have resorted to coastline mapping to improve previous coastline import. I have completed several islands already and my next target is Luzon mainland (already completed most of north-east Luzon up to Ilocos Sur). At first, I thought it should be easy, just load LANDSAT WMS and your good to go. But really it isn't. Because, 1) coastline is a fractal problem [1], at varying zoom-levels you get different details. Using landsat, you need to be at zoom 14-16 to get the most detail. 2) I find it difficult to select, move, and delete nodes of the SRTM generated coastline. You have to use several keystrokes and mouse-clicks. What I do instead is delete several coastline ways and then create a new coastline way. Some questions: 1) How do we map mangrove [2] areas along coastlines? In the "field" mangroves are either inland extending to the coast and even beyond coastline. Do we include mangroves in inter-tidal areas as part of the coastline? 2) Where do coastline and large rivers converge? River deltas [3] is particularly problematic. 3) Sand bars? Siltation areas? Any suggestions on how we map this? Me thinks: coastlines will never be complete because we have so much coastline and the threat of sea-level rise due to climate change [1] http://library.thinkquest.org/26242/full/ap/ap4.html [2] http://en.wikipedia.org/wiki/Mangroves [3] http://en.wikipedia.org/wiki/River_delta -- cheers, maning -- "Freedom is still the most radical idea of all" -N.Branden wiki: http://esambale.wikispaces.com/ blog: http://epsg4253.wordpress.com/ -- ___ talk-ph mailing list talk-ph@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ph
[talk-ph] Mystery Building.
This has been bugging me for sometime, and I suddenly realised that there might be someone in OSM PH who knows the answer. I live in Kingswood: http://openstreetmap.com/?lat=14.567079&lon=121.012242&zoom=18&layers=B000FTF When I look due North from my building I see two tall buildings on the skyline, and I can't figure out what they are. Here is a picture http://dl.getdropbox.com/u/274900/DSCN1355.JPG Off the photo to the right, is Ortigas. These two buildings seem to be about the same distance from me as Ortigas eg. St Francis. This puts them about 5km away from me, so somewhere near Santa Mesa PNR station. Any ideas what they are? Happy Easter by the way. Jim -- datalude: information security e: j...@datalude.com Philippines: +63 2 403 1311 / mob: +63 920 912 5830 Hong Kong: +852 9100 7586 w: http://www.datalude.com/ ___ talk-ph mailing list talk-ph@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ph
Re: [talk-ph] Yahoo!'s satellite imagery in Makati CBD is not good enough
Eugene, Try to can gain access to adjacent villages (eg. bel-air, urdaneta village, san antonio village, san lorenzo) where there are no tall buildings (eg. less than 500m-1km away from CBD). The technique is to get multiple gps tracklogs (carefully taken, slowly driving in the middle of the roads) back and forth, criss-crossing these narrower roads of the residential subdivisions. You'll get fairly accurate (unobstructed) gps traces here, and they're so near your target area (the CBD). The resulting tracklogs in and around these villages will be your reference lines for correcting the traces on the CBD itself. First step: trace over the satellite images inside these residential subdivisions together with CBD (up to the portion of the anomalous image area only), then upload to OSM. On a separate layer in JOSM, drag and calibrate these traces (both adjacent residential subd and the nearer portion of CBD) over the layer of your gps tracklog of the subdivision. Save your work. Use this same technique on the opposite portions of the CBD (using another adjacent subdivision as reference), until all portions of your gps-calibrated traces meet along the anomalous satellite images of the CBD. Use a different color of line (per layer) of your CBD portions, so they won't visually mix up when you try assemble and combine all into a single layer later. Once you combine the CBD traces into a single layer in JOSM, get the best compromise (by redrawing and stitching your different CBD portions) using the natural-geometric shapes and alignments of the roads. If it looks good (not crooked), then it must be fairly accurate. What you'll get is a very good gps-aligned CBD map-trace, without necessarily trying to collect gps tracklogs on the urban canyons of the CBD itself. The only problem is how to get inside the exclusive subdivisions on a mountain bike or a car (with your gps), without alarming the guards. Roaming around is normally prohibited, unless you are a resident of the place. :-) NOTE: on your suggestion to use "top of the building" for gps-reference waypoints, it won't work. You'll notice that the satellite images of most tall buildings are not vertically straight (buildings look like 3-D images swaying to one side). It's roof-top does not necessarily correspond to the building's footprint at street-level (on the satellite image). Therefore, GPS data must be taken only at street level (if you will be using these data along side your satellite traces). On similar case, you must also be careful in tracing roads near a steep hill or mountain. Tracing roads with "greatly-varying altitudes" won't give you accurate data. I noticed this problem years ago when my "carefully-taken gps tracklogs" from the lowlands of Tanay Rizal (along Sampaloc Road) zig-zaging all the way up to the upper portion of Sampaloc Tanay, won't fit the road shape on Google Earth's satellite images. Same case for OSM tracing. I realized that I must chop my road traces into shorter portions, then align them independently to the actual gps tracklogs every few hundred meters or kilometer (depending on how rolling the terrains are). Multiple GPS tracks are still the best reference/s for actual positions (and offsettings); but as to actual "road shapes and geometries" of an area with the same/common road elevation, our "handheld gps" tracklogs can't beat traces over satellite images. What-you-see-is-what-you-get :-) BTW, this technique is also good for tracing (and calibrating) very wide road (10-lanes) such as EDSA or C-5 or NLEX. You can't legally slow down and choose a lane in the multi-lane EDSA to collect reference tracks in tracing EDSA itself or it's vicinity. It is best to get the gps reference tracklogs from narrow (parallel and perpendicular) roads on the sides of EDSA (or C-5). Again, never use tracklog taken from very wide roads like EDSA, Commonwealth, NLEX and alikes, as reference tracklogs for your city map (satellite) traces, unless we have no choice like in the rural areas (eg. SCTEX traces - with no side roads nearby) Cheers, Rally On Thu, Apr 9, 2009 at 8:40 PM, Eugene Alvin Villar wrote: > > > On Thu, Apr 9, 2009 at 7:31 PM, D Tucny wrote: > >> 2009/4/9 Mike Collinson >> >> At 11:26 AM 9/04/2009, Eugene Alvin Villar wrote: >>> >Hi all, >>> > >>> >I was doing some cleaning up and some building mapping in the Makati CBD >>> area and I noticed that the satellite imagery in Yahoo! (provided by GeoEye) >>> has some really bad stitching (multiple satellite imagery were stitched into >>> one "seamless" mosaic). One particularly bad example is that Rufino St. >>> (Herrera) is broken along Ayala Avenue. The stitching of the imagery seems >>> to be along Ayala Avenue and Buendia. If you'll check out the parts of >>> Buendia near the RCBC Plaza, you'll notice that there are two shadow images >>> of Buendia there. >>> > >>> >I think this means that the data in the Makati CBD area might be quite >>> off in some parts. I think that
Re: [talk-ph] just a thought OSM Philippines mini-conference
Sure what do we need here, I have no problem discussing Boracay though it might be more fun to have Jim join in and explain his 'fun' adventure of mapping Boracay :) Andre ___ talk-ph mailing list talk-ph@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ph
Re: [talk-ph] Yahoo!'s satellite imagery in Makati CBD is not good enough
On Thu, Apr 9, 2009 at 7:31 PM, D Tucny wrote: > 2009/4/9 Mike Collinson > > At 11:26 AM 9/04/2009, Eugene Alvin Villar wrote: >> >Hi all, >> > >> >I was doing some cleaning up and some building mapping in the Makati CBD >> area and I noticed that the satellite imagery in Yahoo! (provided by GeoEye) >> has some really bad stitching (multiple satellite imagery were stitched into >> one "seamless" mosaic). One particularly bad example is that Rufino St. >> (Herrera) is broken along Ayala Avenue. The stitching of the imagery seems >> to be along Ayala Avenue and Buendia. If you'll check out the parts of >> Buendia near the RCBC Plaza, you'll notice that there are two shadow images >> of Buendia there. >> > >> >I think this means that the data in the Makati CBD area might be quite >> off in some parts. I think that we need to supplement this with some really >> good GPS traces (the existing uploaded GPS traces are quite noisy) but the >> problem is the urban canyon effect that makes GPS a bit ineffective in this >> area. >> > >> >What do you guys think? >> >> I tried GPS mapping in Makati CBD before the imagery was available and >> found the GPS quality just awful, you are very polite :-) . I had a similar >> problem in Sydney CBD coupled with very oblique aerial imagery that obscures >> many of the roads. The best solution I came up with was to wander about and >> take lots of digital photographs down streets and then iteratively edit the >> map to get relative position looking right against the photos with the few >> spots of good imagery and GPS as a control for absolute position. >> >> Mike >> > > If it's possible to get onto the roof of some of the buildings, you could > get some longish term averaged GPS fixes, and, if you can get ontop of some > of the tall buildings, some aerial photos :) > > The urban canyon effect is going to pretty much rule out getting 'really > good GPS traces' as you'll notice that doing everything you can to get good > signal, the trace will still be all over the place... Maybe in a few years > when GPSrs are better and you can use Gallileo and the US GPS together then > you'll be able to get something half decent, but, for now, creative thinking > and as Mike says, plenty of photos are probably the only way to get a > reasonable level of accuracy... > > d > I actually thought about going to the rooftops of selected buildings to get absolute fixes for these points. Then lay out everything else relatively. But knowing about paranoid security, it'll be hard to access the rooftops of the right buildings. :-P I'll do some research on which buildings are generally access=permissive to the rooftop. :-) Eugene / seav ___ talk-ph mailing list talk-ph@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ph
Re: [talk-ph] Yahoo!'s satellite imagery in Makati CBD is not good enough
2009/4/9 Mike Collinson > At 11:26 AM 9/04/2009, Eugene Alvin Villar wrote: > >Hi all, > > > >I was doing some cleaning up and some building mapping in the Makati CBD > area and I noticed that the satellite imagery in Yahoo! (provided by GeoEye) > has some really bad stitching (multiple satellite imagery were stitched into > one "seamless" mosaic). One particularly bad example is that Rufino St. > (Herrera) is broken along Ayala Avenue. The stitching of the imagery seems > to be along Ayala Avenue and Buendia. If you'll check out the parts of > Buendia near the RCBC Plaza, you'll notice that there are two shadow images > of Buendia there. > > > >I think this means that the data in the Makati CBD area might be quite off > in some parts. I think that we need to supplement this with some really good > GPS traces (the existing uploaded GPS traces are quite noisy) but the > problem is the urban canyon effect that makes GPS a bit ineffective in this > area. > > > >What do you guys think? > > I tried GPS mapping in Makati CBD before the imagery was available and > found the GPS quality just awful, you are very polite :-) . I had a similar > problem in Sydney CBD coupled with very oblique aerial imagery that obscures > many of the roads. The best solution I came up with was to wander about and > take lots of digital photographs down streets and then iteratively edit the > map to get relative position looking right against the photos with the few > spots of good imagery and GPS as a control for absolute position. > > Mike > If it's possible to get onto the roof of some of the buildings, you could get some longish term averaged GPS fixes, and, if you can get ontop of some of the tall buildings, some aerial photos :) The urban canyon effect is going to pretty much rule out getting 'really good GPS traces' as you'll notice that doing everything you can to get good signal, the trace will still be all over the place... Maybe in a few years when GPSrs are better and you can use Gallileo and the US GPS together then you'll be able to get something half decent, but, for now, creative thinking and as Mike says, plenty of photos are probably the only way to get a reasonable level of accuracy... d ___ talk-ph mailing list talk-ph@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ph
Re: [talk-ph] Yahoo!'s satellite imagery in Makati CBD is not good enough
At 11:26 AM 9/04/2009, Eugene Alvin Villar wrote: >Hi all, > >I was doing some cleaning up and some building mapping in the Makati CBD area >and I noticed that the satellite imagery in Yahoo! (provided by GeoEye) has >some really bad stitching (multiple satellite imagery were stitched into one >"seamless" mosaic). One particularly bad example is that Rufino St. (Herrera) >is broken along Ayala Avenue. The stitching of the imagery seems to be along >Ayala Avenue and Buendia. If you'll check out the parts of Buendia near the >RCBC Plaza, you'll notice that there are two shadow images of Buendia there. > >I think this means that the data in the Makati CBD area might be quite off in >some parts. I think that we need to supplement this with some really good GPS >traces (the existing uploaded GPS traces are quite noisy) but the problem is >the urban canyon effect that makes GPS a bit ineffective in this area. > >What do you guys think? I tried GPS mapping in Makati CBD before the imagery was available and found the GPS quality just awful, you are very polite :-) . I had a similar problem in Sydney CBD coupled with very oblique aerial imagery that obscures many of the roads. The best solution I came up with was to wander about and take lots of digital photographs down streets and then iteratively edit the map to get relative position looking right against the photos with the few spots of good imagery and GPS as a control for absolute position. Mike ___ talk-ph mailing list talk-ph@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ph
[talk-ph] Yahoo!'s satellite imagery in Makati CBD is not good enough
Hi all, I was doing some cleaning up and some building mapping in the Makati CBD area and I noticed that the satellite imagery in Yahoo! (provided by GeoEye) has some really bad stitching (multiple satellite imagery were stitched into one "seamless" mosaic). One particularly bad example is that Rufino St. (Herrera) is broken along Ayala Avenue. The stitching of the imagery seems to be along Ayala Avenue and Buendia. If you'll check out the parts of Buendia near the RCBC Plaza, you'll notice that there are two shadow images of Buendia there. I think this means that the data in the Makati CBD area might be quite off in some parts. I think that we need to supplement this with some really good GPS traces (the existing uploaded GPS traces are quite noisy) but the problem is the urban canyon effect that makes GPS a bit ineffective in this area. What do you guys think? Eugene / seav -- http://vaes9.codedgraphic.com ___ talk-ph mailing list talk-ph@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ph
