[Talk-in] Need guidance in launching a HOT project in Bangalore for mapping the lakes

Yogesh yogesh at karnatakaeducation.org.in
Thu Nov 19 13:01:52 UTC 2020

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 -

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.planemad at gmail.com
> <mailto:arun.planemad at gmail.com>> wrote:
>     On Thu, Nov 12, 2020 at 5:10 AM Nagesh Aras
>     <nagesh.sa.blr at gmail.com <mailto:nagesh.sa.blr at 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 
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