25 Jun
2008
25 Jun
'08
8:09 a.m.
Hey,
Since many people on this list have attended workshops or
even done some mapping/tracing work, I thought I would ask some
questions here -
1) Suppose you are walking on a particular street - 2 way
street even - you encounter a few shops - say a big Sweet and Snacks /
Hotel / School / anything, on the same street. Now how do you put
those on the maps while GPS tracking and then tracing the map on the
computer?
I mean, the to reach the shop, you have to walk good 5
meters or such - at times - depending on width of foot path or such.
Now those paths are not roads really, and they can vary from place to
place. How to tackle such offsets ?
2) Suppose you have tracked certain part of your town or
your route from your home to airport near your city. Then you fly to
another city and then restart the GPS device. At that point the device
generally has to re-initiate itself to capture/detect the satellites (
which it has to do anyway incase you turn off and then switch on a gps
device - atleast in some devices that I have seen ). Anyway after it
has done that, it calculates the Longitude and Latitude and hence the
current position. What happens in this case is, the GPS device draws a
straight line from City A to City B. Is there a way to avoid that /
tackle that ?
Any pointers ? Thanks in advance.
Cheers!
Pradeepto
--
The KDE Project : http://www.kde.org
KDE India : http://in.kde.org
Mailing List : http://mail.kde.org/mailman/listinfo/kde-india
25 Jun
25 Jun
8:20 a.m.
hi !
On Wed, Jun 25, 2008 at 1:39 PM, Pradeepto Bhattacharya
<pradeeptob(a)gmail.com> wrote:
Hey,
Since many people on this list have attended workshops or
even done some mapping/tracing work, I thought I would ask some
questions here -
1) Suppose you are walking on a particular street - 2 way
street even - you encounter a few shops - say a big Sweet and Snacks /
Hotel / School / anything, on the same street. Now how do you put
those on the maps while GPS tracking and then tracing the map on the
computer?
Mark what you want as waypoints .so its always a good decision to
carry a notepad and a pen while mapping.
I mean, the to reach the shop, you have to walk good 5
meters or such - at times - depending on width of foot path or such.
Now those paths are not roads really, and they can vary from place to
place. How to tackle such offsets ?
Offsets can only be tackle when you are
actually editing the track for
maps . JOSM , potlaych , mapnik all provide presets for this .again
pen and paper comes to help .
2) Suppose you have tracked certain part of your town or
your route from your home to airport near your city. Then you fly to
another city and then restart the GPS device. At that point the device
generally has to re-initiate itself to capture/detect the satellites (
which it has to do anyway incase you turn off and then switch on a gps
device - atleast in some devices that I have seen ). Anyway after it
has done that, it calculates the Longitude and Latitude and hence the
current position. What happens in this case is, the GPS device draws a
straight line from City A to City B. Is there a way to avoid that /
tackle that ?
well just dont put that part while editing the tracks/routes . its
always better to mark waypoints of imporatnt cities in between routes
. atleast thats what i did from delhi to kolkata and off course take
help of yahoo maps as the collaborate with OSM with thsi regard . more
details can be found at osm-talk list
Any pointers ? Thanks in advance.
Cheers!
Pradeepto
happy mapping
--
Regards
Subhodip Biswas
Fedora Ambassador
West Bengal , India
GPG key : FAEA34AB
Server : pgp.mit.edu
http://subhodipbiswas.wordpress.com
http:/www.fedoraproject.org/wiki/SubhodipBiswas
1:10 p.m.
Hi,
On Wed, Jun 25, 2008 at 1:50 PM, Subhodip Biswas
<subhodipbiswas(a)gmail.com> wrote:
well just dont put that part while editing the tracks/routes . its
Oki doki.
always better to mark waypoints of imporatnt cities in
between routes
. atleast thats what i did from delhi to kolkata and off course take
I would be very scared if you were in flying in the
same plane as that of me ;). It generally is advised by the crew to
turn off electronic devices after the plane's doors are closed /
during take off / landing and communication devices are a strict no-no
throught out the flight. And even if it were allowed, it would
slightly difficult to mark way points from few thousand feet ;)
The question was based on the fact that, while flying a
device would have to switched off until the destination has been
reached. Anyway, thanks to you and JTD, I got the idea now.
Cheers!
Pradeepto
--
The KDE Project : http://www.kde.org
KDE India : http://in.kde.org
Mailing List : http://mail.kde.org/mailman/listinfo/kde-india
26 Jun
26 Jun
5:44 a.m.
On Wednesday 25 Jun 2008 18:40, Pradeepto Bhattacharya wrote:
I would be very scared if you were in flying in the
same plane as that of me ;). It generally is advised by the crew to
turn off electronic devices after the plane's doors are closed /
during take off / landing and communication devices are a strict
no-no throught out the flight. And even if it were allowed, it
would slightly difficult to mark way points from few thousand feet
;)
That is a load of rubbish by the AHs who man these flights and make
the rules. You would not have survived a plane with navigation
equipment so poorly shielded against rfi. Every vsat terminal blasts
several watts of rf in a tightly focussed beam. Your pissy phone can
barely emit 1 watt and that too omni directional. Most other battery
powered equipment cant even disturb the reception of an am reciever.
And dont forget TV and FM stations - several Kilowatts for tv 15KW
being the norm, 400W for FM.
Next time you can give the airhostess a lesson in RF transmissions ;-)
--
Rgds
JTD
25 Jun
25 Jun
9:19 a.m.
On Wednesday 25 Jun 2008 13:39, Pradeepto Bhattacharya wrote:
Hey,
Since many people on this list have attended workshops or
even done some mapping/tracing work, I thought I would ask some
questions here -
1) Suppose you are walking on a particular street - 2 way
street even - you encounter a few shops - say a big Sweet and
Snacks / Hotel / School / anything, on the same street. Now how do
you put those on the maps while GPS tracking and then tracing the
map on the computer?
I mean, the to reach the shop, you have to walk good
5 meters or such - at times - depending on width of foot path or
such. Now those paths are not roads really, and they can vary from
place to place. How to tackle such offsets ?
GPS data is accurate to 2.5 mtr in a few, 5mtr for most under ideal
conditions. Usually 10 Mtr. So you are anyway off by a few meters.
For the accuracies that you are talking of you would require survey
quality gps AND DGPS with correction data for your locality.
2) Suppose you have tracked certain part of your town or
your route from your home to airport near your city. Then you fly
to another city and then restart the GPS device. At that point the
device generally has to re-initiate itself to capture/detect the
satellites ( which it has to do anyway incase you turn off and then
switch on a gps device - atleast in some devices that I have seen
). Anyway after it has done that, it calculates the Longitude and
Latitude and hence the current position. What happens in this case
is, the GPS device draws a straight line from City A to City B. Is
there a way to avoid that / tackle that ?
That is a function of the handheld (which is a small computer with all
sorts of features attached to an internal gps) not a function of the
gps. You will have to check your particular handheld gps user manual
on how to stop and start new traces.
Any pointers ? Thanks in advance.
Cheers!
Pradeepto
--
The KDE Project : http://www.kde.org
KDE India : http://in.kde.org
Mailing List : http://mail.kde.org/mailman/listinfo/kde-india
--
Rgds
JTD
12:58 p.m.
Hey,
On Wed, Jun 25, 2008 at 2:49 PM, jtd <jtd(a)mtnl.net.in> wrote:
GPS data is accurate to 2.5 mtr in a few, 5mtr for most under ideal
conditions. Usually 10 Mtr. So you are anyway off by a few meters.
For the accuracies that you are talking of you would require survey
quality gps AND DGPS with correction data for your locality.
Hmm, not sure about different GPS models, the one I have
used I noticed that it could give me 2 different ( parallel ) tracks
for walking on extreme sides of a 2 way road and that too in New
Panvel where the roads are far less wide compared to those in New
Delhi ;).
What is "DGPS with correction data for your locality." ?
Cheers!
Pradeepto
--
The KDE Project : http://www.kde.org
KDE India : http://in.kde.org
Mailing List : http://mail.kde.org/mailman/listinfo/kde-india
26 Jun
26 Jun
6:06 a.m.
On Wednesday 25 Jun 2008 18:28, Pradeepto Bhattacharya wrote:
Hmm, not sure about different GPS models,
the one I have
used I noticed that it could give me 2 different ( parallel )
tracks for walking on extreme sides of a 2 way road and that too in
New Panvel where the roads are far less wide compared to those in
New Delhi ;).
The two line are relative to itself. I absolute terms you still dont
know if the lines are accurate. If you take another model of gps,
there will (proly) be a slight difference. If you take the reading
under cloudy skies there may be difference.
What is "DGPS with correction data for your locality." ?
Differential GPS. A method of correcting gps errors. Other newer
methods are WAAS (Wide Area Augmentation System) and SBAS (Satellite
Based Augmentation Systems).
http://www.kowoma.de/en/gps/waas_egnos.htm
GPS systems have errors due to atmospheric / ionospheric delays,
reflected signals, timing inaccuracies and sattelite drift. Theses
errors (except atmospheric) are nearly the same for an area of a few
100 sqKm. So if you can fix a location triangulated by standard
surveying techniques and then take the difference with the one shown
by the gps, you have an error correction factor available. Broadcast
this factor by radio or over the net or by satellite. Recieve the
error factor, feed it to the gps and correct your gps reading.
Very useful when surveying and mapping - given the astronomical prices
of real estate.
--
Rgds
JTD
27 Jun
27 Jun
5:33 a.m.
On 26-Jun-08, at 11:36 AM, jtd wrote:
Very useful when surveying and mapping - given the
astronomical prices
of real estate.
better to use a laser range finder for this - gps wont cut it
--
regards
Kenneth Gonsalves
Associate, NRC-FOSS
lawgon(a)au-kbc.org
http://nrcfosshelpline.in/code/
7:45 a.m.
On Friday 27 Jun 2008 11:03, Kenneth Gonsalves wrote:
On 26-Jun-08, at 11:36 AM, jtd wrote:
Sort of True. Survey quality gps will give you repeatability - the
offset will be consistent and the distance between two points over a
few Km will be accurate. But the position wrt to a standard survey
may be way off. Thus results (conventional survey or gps) are open to
interpretation.
--
Rgds
JTD
Very useful when surveying and mapping - given
the astronomical
prices of real estate.
better to use a laser range finder for this - gps wont cut it
28 Jun
28 Jun
5:12 a.m.
On 27-Jun-08, at 1:15 PM, jtd wrote:
I tried to do a couple of golf courses with gps - total failure. With
the laser range finder (and not a very expensive one, I was able to
get accuracy within a yard - which is acceptable for a golf course.
--
regards
Kenneth Gonsalves
Associate, NRC-FOSS
lawgon(a)au-kbc.org
http://nrcfosshelpline.in/code/
better to use a laser range finder for this - gps wont cut it
Sort of True. Survey quality gps will give you repeatability - the
offset will be consistent and the distance between two points over a
few Km will be accurate. But the position wrt to a standard survey
may be way off. Thus results (conventional survey or gps) are open to
interpretation.
6:07 a.m.
On Saturday 28 Jun 2008 10:42, Kenneth Gonsalves wrote:
On 27-Jun-08, at 1:15 PM, jtd wrote:
I tried to do a couple of golf courses with gps - total failure.
With the laser range finder (and not a very expensive one, I was
able to get accuracy within a yard - which is acceptable for a golf
course.
You should get upto 2.5 m with a 32 ch device. Of course only twelve
are used. but it picks a good mix of overhead and horizon sats. try
by keeping the reciever still on the ground.
For higher accuracies survey quality gps. You should get accuracy of 1
mm/Km.
Also by fixing two points accurately on the periphery by non gps
means, you could get a deviation figure and correct your readings.
You will have to take the correction every few hrs as ionospheric
delays vary with sun activity. I have only a vague understanding of
the issues involved so dont bet the house on data from this thread.
--
Rgds
JTD
better to
use a laser range finder for this - gps wont cut it
Sort of True. Survey quality gps will give you repeatability -
the offset will be consistent and the distance between two points
over a few Km will be accurate. But the position wrt to a
standard survey may be way off. Thus results (conventional survey
or gps) are open to interpretation.
6:41 a.m.
On 28-Jun-08, at 11:37 AM, jtd wrote:
--
regards
Kenneth Gonsalves
Associate, NRC-FOSS
lawgon(a)au-kbc.org
http://nrcfosshelpline.in/code/
Also by fixing two points accurately on the periphery
by non gps
means,
how is this done? I am told that in America there are markers
everywhere giving reference points. The only one in India I have seen
is at St Thomas Mount where they started the survey of India.
you could get a deviation figure and correct your
readings.
You will have to take the correction every few hrs as ionospheric
delays vary with sun activity.
I tried marking the main fountain in Ooty - walked around it 3 times
and marked the waypoints. They were all over the place. I was using a
garmin device and it was showing accuracy of 30-35 metres on that day.
1:05 p.m.
On Saturday 28 Jun 2008 12:11, Kenneth Gonsalves wrote:
On 28-Jun-08, at 11:37 AM, jtd wrote:
> Also by fixing two points accurately on the periphery by non gps
> means,
http://www.iers.org/
Essentially use star data to locate a point on earth, then reference
that to WGS84.
About Indian geodectic state of affairs
http://www.mycoordinates.org/geodetic-infrastructure.php
Might be good idea to contact the Survey of India, Hyderabad.
But if you do not need the absolute coordinates. Just mark two points
1Km apart accurately aligned NS. This is your baseline. Note a few
coordinates with a gps placed flat on the ground. Calculate the
distance between the coords. The error is your correction factor.
Also available on the net is rinex data which gives you the
ionospheric variation for a particular area, from which one can
estimate error.
how is this done? I am told that in America there are markers
everywhere giving reference points. The only one in India I have
seen is at St Thomas Mount where they started the survey of India.
Yes. A steel rod fixed in concrete in the ground. also known as a
geodectic reference point.
> you could get a deviation figure and correct your readings.
> You will have to take the correction every few hrs as ionospheric
> delays vary with sun activity.
http://www.precision-gps.org./Mathematics.htm
I tried marking the main fountain in Ooty - walked
around it 3
times and marked the waypoints. They were all over the place. I was
using a garmin device and it was showing accuracy of 30-35 metres
on that day.
That is because it's proly 12 channel, has an internal antenna and no
waas / sbas.
Since India has launched GIS sats. I am inclined towards the fact that
geodectic info must be available either at isro or Survey of India.
Perhaps an approach by some institution (HBCSE, AU-KBC) may prise it
out.
--
Rgds
JTD
2 p.m.
On 28-Jun-08, at 6:35 PM, jtd wrote:
About Indian geodectic state of affairs
http://www.mycoordinates.org/geodetic-infrastructure.php
omg - I didnt think it was this bad - we have a lot of work ahead of us
--
regards
Kenneth Gonsalves
Associate, NRC-FOSS
lawgon(a)au-kbc.org
http://nrcfosshelpline.in/code/
30 Jun
30 Jun
5:27 a.m.
On Saturday 28 Jun 2008 19:30, Kenneth Gonsalves wrote:
On 28-Jun-08, at 6:35 PM, jtd wrote:
Indeed. Infact several high security areas blocked by googlemaps after
the rukus by the indian government are areas several 10s of Km off
mark. Result - adjoining villages and roads are not visible and the
high security area nicely exposed. Our official maps must be a real
disaster.
--
Rgds
JTD
About Indian geodectic state of affairs
http://www.mycoordinates.org/geodetic-infrastructure.php
omg - I didnt think it was this bad - we have a lot of work ahead
of us
26 Jun
26 Jun
3:06 a.m.
On 25-Jun-08, at 1:39 PM, Pradeepto Bhattacharya wrote:
1) Suppose you are walking on a particular street -
2 way
street even - you encounter a few shops - say a big Sweet and Snacks /
Hotel / School / anything, on the same street. Now how do you put
those on the maps while GPS tracking and then tracing the map on the
computer?
paper and pen
I mean, the to reach the shop, you have to walk good 5
meters or such - at times - depending on width of foot path or such.
Now those paths are not roads really, and they can vary from place to
place. How to tackle such offsets ?
measure it
2) Suppose you have tracked certain part of your town or
your route from your home to airport near your city. Then you fly to
another city and then restart the GPS device. At that point the device
generally has to re-initiate itself to capture/detect the satellites (
which it has to do anyway incase you turn off and then switch on a gps
device - atleast in some devices that I have seen ). Anyway after it
has done that, it calculates the Longitude and Latitude and hence the
current position. What happens in this case is, the GPS device draws a
straight line from City A to City B. Is there a way to avoid that /
tackle that ?
no way to avoid it - delete the line
--
regards
Kenneth Gonsalves
Associate, NRC-FOSS
lawgon(a)au-kbc.org
http://nrcfosshelpline.in/code/
3:56 a.m.
Hi,
On Thu, Jun 26, 2008 at 8:36 AM, Kenneth Gonsalves <lawgon(a)au-kbc.org> wrote:
That might be possible ( if at all ) if I am doing nothing
else but mapping, but not when I am on my morning/evening walk or just
going from one place to another in a vehicle/train/whatever ( and
mapping on the sidelines ) and can't stop to do such measurements.
Plus, what would be the use of such measurements anyway? My concern
with offsets is the accuracy of the resultant map and positions of
waypoints ( shops/schools etc ) on the map.
Cheers!
Pradeepto
--
The KDE Project : http://www.kde.org
KDE India : http://in.kde.org
Mailing List : http://mail.kde.org/mailman/listinfo/kde-india
On 25-Jun-08, at 1:39 PM, Pradeepto Bhattacharya wrote:
Actually some devices can store names of the way point.
That was not the problem at all. The problem is about offsets and
resultant accuracy of maps.
1) Suppose you are walking on a particular
street - 2 way
street even - you encounter a few shops - say a big Sweet and Snacks /
Hotel / School / anything, on the same street. Now how do you put
those on the maps while GPS tracking and then tracing the map on the
computer?
paper and pen
I mean, the to reach the shop, you have to walk good 5
meters or such - at times - depending on width of foot path or such.
Now those paths are not roads really, and they can vary from place to
place. How to tackle such offsets ?
measure it
4:09 a.m.
On 26-Jun-08, at 9:26 AM, Pradeepto Bhattacharya wrote:
if you cant, dont - go do something else and leave mapping to people
with more commitment
--
regards
Kenneth Gonsalves
Associate, NRC-FOSS
lawgon(a)au-kbc.org
http://nrcfosshelpline.in/code/
measure it
That might be possible ( if at all ) if I am doing nothing
else but mapping, but not when I am on my morning/evening walk or just
going from one place to another in a vehicle/train/whatever ( and
mapping on the sidelines ) and can't stop to do such measurements.
4:10 a.m.
Hi,
On Thu, Jun 26, 2008 at 9:39 AM, Kenneth Gonsalves <lawgon(a)au-kbc.org> wrote:
On 26-Jun-08, at 9:26 AM, Pradeepto Bhattacharya wrote:
if you cant, dont - go do something else and leave mapping to people
with more commitment
I see why there was a reason to get personal or rude at
all. I was honestly asking for tips on how things are done.
Cheers!
Pradepeto
--
The KDE Project : http://www.kde.org
KDE India : http://in.kde.org
Mailing List : http://mail.kde.org/mailman/listinfo/kde-india
measure
it
That might be possible ( if at all ) if I am doing nothing
else but mapping, but not when I am on my morning/evening walk or just
going from one place to another in a vehicle/train/whatever ( and
mapping on the sidelines ) and can't stop to do such measurements.
4:23 a.m.
On 26-Jun-08, at 9:40 AM, Pradeepto Bhattacharya wrote:
On Thu, Jun 26, 2008 at 9:39 AM, Kenneth Gonsalves
<lawgon@au-
kbc.org> wrote:
nothing rude or personal here - it is just that mapping is also hard
work. 2-3 metres inaccuracy in the devices means physically getting
down and working at accuracy. Indians? working? taking trouble?
sheesh - *that* is rude.
--
regards
Kenneth Gonsalves
Associate, NRC-FOSS
lawgon(a)au-kbc.org
http://nrcfosshelpline.in/code/
On 26-Jun-08, at 9:26 AM, Pradeepto Bhattacharya wrote:
if you cant, dont - go do something else and leave mapping to people
with more commitment
I see why there was a reason to get personal or rude at
all. I was honestly asking for tips on how things are done. measure
it
That might be possible ( if at all ) if I am doing
nothing
else but mapping, but not when I am on my morning/evening walk or
just
going from one place to another in a vehicle/train/whatever ( and
mapping on the sidelines ) and can't stop to do such measurements.
4:49 a.m.
On 26-Jun-08, at 9:53 AM, Kenneth Gonsalves wrote:
--
regards
Kenneth Gonsalves
Associate, NRC-FOSS
lawgon(a)au-kbc.org
http://nrcfosshelpline.in/code/
On 26-Jun-08, at 9:40 AM, Pradeepto Bhattacharya wrote:
and looking at panvel - http://www.openstreetmap.org/edit?
lat=11.404&lon=76.713&zoom=11, nothing here. You could atleast trace
out that river (dont worry about accuracy)
On Thu, Jun 26, 2008 at 9:39 AM, Kenneth
Gonsalves <lawgon@au-
kbc.org> wrote:
nothing rude or personal here - it is just that mapping is also hard
work. 2-3 metres inaccuracy in the devices means physically getting
down and working at accuracy. Indians? working? taking trouble?
sheesh - *that* is rude.
On 26-Jun-08, at 9:26 AM, Pradeepto Bhattacharya wrote:
I see why there was a reason to get personal or rude at
all. I was honestly asking for tips on how things are done. > measure it
That might be possible ( if at all ) if I am doing
nothing
else but mapping, but not when I am on my morning/evening walk or
just
going from one place to another in a vehicle/train/whatever ( and
mapping on the sidelines ) and can't stop to do such measurements.
if you cant, dont - go do something else and leave mapping to people
with more commitment
8:41 a.m.
On Thursday 26 Jun 2008 09:53, Kenneth Gonsalves wrote:
nothing rude or personal here - it is just that mapping is also
hard work. 2-3 metres inaccuracy in the devices means physically
getting down and working at accuracy. Indians? working? taking
trouble? sheesh - *that* is rude.
http://www.gisdevelopment.net/technology/gps/techgp0022.htm
IIT apparently has implemented a SBAS repo. If some one could get it
published on the web.
Would reduce errors very substantially. And save some labour too.
--
Rgds
JTD
9:05 a.m.
digging in google threw this up
http://igs.bkg.bund.de/admin/db/db_edit.php?id=1004&table=Station
One station in B'lore for the whole country. Way to go.
Wonder what are we launching gis satellites for?
--
Rgds
JTD
7 a.m.
Pradeepto Bhattacharya wrote:
That might be possible ( if at all ) if I am doing
nothing
else but mapping, but not when I am on my morning/evening walk or just
going from one place to another in a vehicle/train/whatever ( and
mapping on the sidelines ) and can't stop to do such measurements.
Plus, what would be the use of such measurements anyway? My concern
with offsets is the accuracy of the resultant map and positions of
waypoints ( shops/schools etc ) on the map.
Is there an easier way of mapping by using high resolution maps from
googlemaps or any other provider and converting them into drawings. All
the street lamp tops as well as building tops can be painted with
special identification code patterns that can be observed from space and
can be marked clearly in the satt. images. This reduces the trouble of
people having to manually walk everywhere with a device in hand. A
software that can convert the optical pattern code into text,
automatically adds relevant content into the converted maps. Just my 2p.
"Laziness is the mother of innovation."
--
Regards,
Rony.
GNU/Linux !
No Viruses
No Spyware
Only Freedom.
27 Jun
27 Jun
5:35 a.m.
On 26-Jun-08, at 12:30 PM, Rony wrote:
Pradeepto Bhattacharya wrote:
copyright problems with google maps - we have to make do with yahoo
images
--
regards
Kenneth Gonsalves
Associate, NRC-FOSS
lawgon(a)au-kbc.org
http://nrcfosshelpline.in/code/
That might be possible ( if at all ) if I am
doing nothing
else but mapping, but not when I am on my morning/evening walk or
just
going from one place to another in a vehicle/train/whatever ( and
mapping on the sidelines ) and can't stop to do such measurements.
Plus, what would be the use of such measurements anyway? My concern
with offsets is the accuracy of the resultant map and positions of
waypoints ( shops/schools etc ) on the map.
Is there an easier way of mapping by using high resolution maps from
googlemaps or any other provider
5:57 p.m.
Kenneth Gonsalves wrote:
On 26-Jun-08, at 12:30 PM, Rony wrote:
Thats not a problem. The main part of the solution is to optically mark
lamp posts and building tops with optical patterns that represent coded
text. The lamp posts provide the road path and buildings the content.
Since the satt. is already in space, the only manual labour is to plant
plastic or wooden sheets painted with pre-programmed codes. The satt.
camera image is then processed in something like an OCR and we get
absolute accurate maps with no errors.
--
Regards,
Rony.
GNU/Linux !
No Viruses
No Spyware
Only Freedom.
Pradeepto Bhattacharya wrote:
copyright problems with google maps - we have to make do with yahoo
images
That might be possible ( if at all ) if I am
doing nothing
else but mapping, but not when I am on my morning/evening walk or
just
going from one place to another in a vehicle/train/whatever ( and
mapping on the sidelines ) and can't stop to do such measurements.
Plus, what would be the use of such measurements anyway? My concern
with offsets is the accuracy of the resultant map and positions of
waypoints ( shops/schools etc ) on the map.
Is there an easier way of mapping by using high resolution maps from
googlemaps or any other provider
7:57 a.m.
On Thursday 26 Jun 2008 12:30, Rony wrote:
Is there an easier way of mapping by using high resolution maps
from googlemaps or any other provider and converting them into
drawings.
Possible except that the images are quite inaccurate. The sats
photograph a swath of the earth's surface. The edges are distorted
and corrected mathematically based on assumptions. Quite often these
assumptions are wrong. And data from two sources will deviate in
weird ways with skews and offsets.
All the street lamp tops as well as building tops can
be
painted with special identification code patterns that can be
the cost of paint would be more than the cost of handing out gpss to
people. Not to mention pollution
observed from space and can be marked clearly in the
satt. images.
This reduces the trouble of people having to manually walk
everywhere with a device in hand. A software that can convert the
optical pattern code into text, automatically adds relevant content
into the converted maps. Just my 2p.
Extremely error prone. Read 1st para.
--
Rgds
JTD
6:02 p.m.
jtd wrote:
On Thursday 26 Jun 2008 12:30, Rony wrote:
It would be similar to maps.google.com images in mixed mode....satt. and
outline with text over it. At very close zooms over small areas, the
curvature of the earth may be easy to correct. Something like an areal
photo from a spy plane. .
--
Regards,
Rony.
GNU/Linux !
No Viruses
No Spyware
Only Freedom.
observed from space and can be marked clearly in
the satt. images.
This reduces the trouble of people having to manually walk
everywhere with a device in hand. A software that can convert the
optical pattern code into text, automatically adds relevant content
into the converted maps. Just my 2p.
Extremely error prone. Read 1st para.
28 Jun
28 Jun
5:55 a.m.
On Friday 27 Jun 2008 23:32, Rony wrote:
jtd wrote:
Wrong. Checkout Surat.
On Thursday 26 Jun 2008 12:30, Rony wrote:
It would be similar to maps.google.com images in mixed
mode....satt. and outline with text over it. At very close zooms
over small areas, observed from space and can be marked clearly in
the satt.
images. This reduces the trouble of people having to manually
walk everywhere with a device in hand. A software that can
convert the optical pattern code into text, automatically adds
relevant content into the converted maps. Just my 2p.
Extremely error prone. Read 1st para. the curvature of the earth may be easy to
correct. Something like an areal photo from a spy plane. .
Its a wrong approach. You can use such a method as a rough guide only.
There are numerous issues with the type of projections, proximity to
the pole etc - rendering a sphere on a flat surface - apart from the
problems with sat imagery.
Basically the pixmaps you see are pre-rendered images from a
geodatabase overlayed with satellite imagery, Out of which you are
trying to create a GIS database. The process is not bidirectional.
You MUST generate an accurate database for substantial areas to have
useable data.
BTW street maps are a minor part of a GIS system.
Real use happens when you can overlay info like disease spreads, water
sheds, insect vectors etc, etc. and come up with a basis to use these
as predictors of problems. Then use these as guides to intervene. e.g
mindless spraying of inseticide to prevent malaria in Mumbai and Navi
mumbai. Is any body checking the effectiveness of such methods and
how it is actually helping the mosquitoes by killing natural
predators (who btw are several orders of magnitude more effective
than ddt / malthion ).
Being directed to the nearest dhaba by googlemaps is great but
ensuring you dont get hepatitis-B on the house is proly a lot better.
The point here is that mapping is a tedious affair. Shortcuts result
in poor quality database which inevitably causes bitrot. Besides the
copyright issues there are technical issues too - both rather
difficult to solve.
Make the extra effort to prevent bitrot and legal hassles.
The FOSS approach is a perfect fit for GIS.
--
Rgds
JTD
6:13 a.m.
On 28-Jun-08, at 11:25 AM, jtd wrote:
The point here is that mapping is a tedious affair.
Shortcuts result
in poor quality database which inevitably causes bitrot. Besides the
copyright issues there are technical issues too - both rather
difficult to solve.
Make the extra effort to prevent bitrot and legal hassles.
The FOSS approach is a perfect fit for GIS.
also do not forget that google imagery, in India anyway is anything
from 1 to 3 years old, depending on the area.
--
regards
Kenneth Gonsalves
Associate, NRC-FOSS
lawgon(a)au-kbc.org
http://nrcfosshelpline.in/code/
7 a.m.
jtd wrote:
The point here is that mapping is a tedious affair. Shortcuts result
in poor quality database which inevitably causes bitrot. Besides the
copyright issues there are technical issues too - both rather
difficult to solve.
Make the extra effort to prevent bitrot and legal hassles.
The FOSS approach is a perfect fit for GIS.
True!
--
Regards,
Rony.
GNU/Linux !
No Viruses
No Spyware
Only Freedom.
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participants (5)
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jtd -
Kenneth Gonsalves -
Pradeepto Bhattacharya -
Rony -
Subhodip Biswas