Hi Nagesh, Sorry for writing in late; If you get your pdf/image maps geo-referenced on mapwarper.net or elsewhere, here's a simple tool you can use to compare them with satellite imagery etc, and also to compare them with each other: https://answerquest.github.io/overlap-custom-side.html
Click at a spot of interest on the map to get exact lat-long-zoom coords for your documentation. The current view there shows two development plan maps of Bangalore that had been geo-referenced and shared by some folks in datameet mailing list some years back. All the best with this project. -- Cheers, Nikhil VJ https://nikhilvj.co.in On Thu, Nov 19, 2020 at 6:35 PM Yogesh <yog...@karnatakaeducation.org.in> wrote: > On 18/11/20 8:31 pm, Nagesh Aras wrote: > > We have multiple maps: > 1. Old paper maps (British era) > 2. Digitized maps > 3. Google map > 4. OpenStreet Map. > > One example is that of the Pattandur lake: > https://drive.google.com/drive/folders/1sHPjk4NqVjB1Opr7Fv6Sj5AvQiCi9JHg?usp=sharing > > The problem is that none of these maps may match with the others. > So how do we proceed, and eliminate differences/doubts? > > Out of copyright British era maps can be geo-referenced over a web map on > Map Warper: https://mapwarper.net/ > > This may not be very accurate but with enough reference points, it can be > matched with others. > > > From the looks of it, it looks like every pair of maps requires a separate > HOT-style project. > (Remote mappers compare the two maps and find differences.) > > > As Arun suggested in his second part, existing lakes survey has to be done > to collect as much data as possible on the ground via paper, gpx traces, > and geotagged pictures of the lakes. All of this can help remote mappers to > chip in for the mapping alongside satellite imagery via HOT tasking manager. > > To get started, I think we can put all of this together on an OSM wiki > page. Each lake can have a sub-page with related links to out of copyright > maps and collected survey data. Have created a wiki page with basic > information that you shared on mailing list here - > https://wiki.openstreetmap.org/wiki/Bangalore_lakes_mapping_project > > Please feel free to modify the title/content of the page as required. > > On Fri, Nov 13, 2020 at 1:01 AM Arun Ganesh <arun.plane...@gmail.com> > wrote: > >> >> >> On Thu, Nov 12, 2020 at 5:10 AM Nagesh Aras <nagesh.sa....@gmail.com> >> wrote: >> >>> Hi all, >>> >>> Several activist groups in Bangalore have come together with the aim of >>> mapping the water system in the city, which includes the lakes, and >>> drainage system. The aim is to digitize thold maps to know what was the >>> original shape and size of the lakes, and then do the local surveys to find >>> out how much of the lake territory is encroached. >>> >>> We would like to set up the online HOT map for this purpose. >>> >>> Can anyone guide us about the steps required for this project? >>> >>> Also, if there are any permissions to be taken, who should I contact? >>> >>> Thanks in advance! >>> Nagesh >>> >> >> This is great! Looks like there are two parts: >> - Digitize old maps: this one is tricky because old maps have various >> quality issues. Vectorizing them might be resource intensive and not too >> useful. Can you share an example of these old maps? >> - Survey existing lakes. This is where OSM can be helpful. To scope this >> out better maybe we should start with one particular lake to test out what >> is the best strategy of satellite image tracing and field survey that will >> work for the accuracy needed. >> >> The OSM India telegram group is fairly active and can be helpful to >> coordinate this in further detail: https://t.me/OSMIndia >> _______________________________________________ >> Talk-in mailing list >> Talk-in@openstreetmap.org >> https://lists.openstreetmap.org/listinfo/talk-in >> > > _______________________________________________ > Talk-in mailing > listTalk-in@openstreetmap.orghttps://lists.openstreetmap.org/listinfo/talk-in > > > -- > Yogi > Sent from an Electronic Device > > _______________________________________________ > Talk-in mailing list > Talk-in@openstreetmap.org > https://lists.openstreetmap.org/listinfo/talk-in >
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