Hi,
I am the developer of the android application "Distance and area measurement", which I know has been discussed to be incorporated into OpenDataKit in the past. I would therefore like to inform you that the application now has been turned into a webpage that should be easy to incorporate through a webview.
/Kristofer Björnson
Just realized that I probably should let you know the address as well
https://www.georuler.com
This is a really neat idea, Kristofer! The challenge of integrating
the web view into Collect is that we don't really have hooks to take
whatever result you get in the web view and get that back to Collect
where it can be persisted. Any ideas on how we'd do that?
Yaw
Maybe we can work something out if it is of interest to you. What kind of
data would you like to have? All GPS coordinates of the path, distance,
area?
/Kristofer Björnson
This is a really neat idea, Kristofer! The challenge of integrating
the web view into Collect is that we don't really have hooks to take
whatever result you get in the web view and get that back to Collect
where it can be persisted. Any ideas on how we'd do that?Yaw
On Tue, Apr 25, 2017 at 12:14 PM, dafer45@gmail.com wrote:
On Tuesday, April 25, 2017 at 5:58:35 PM UTC+2, con...@georuler.com wrote:
Hi,
I am the developer of the android application "Distance and area
measurement", which I know has been discussed to be incorporated into
OpenDataKit in the past. I would therefore like to inform you that the
application now has been turned into a webpage that should be easy to
incorporate through a webview./Kristofer Björnson
Just realized that I probably should let you know the address as well
https://www.georuler.com--
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Maybe we can work something out if it is of interest to you. What kind of
data would you like to have? All GPS coordinates of the path, distance,
area?
FYI - the existing XForms data types (look here
https://opendatakit.github.io/xforms-spec/#data-types) geotrace (line)
and geoshape (polygon) can take your list of GPS coords. Distance and area
would need to be treated differently in the XForm/by ODK Collect, in that
these would probably map - as distinct values - to the existing basic data
type decimal, whose value would then be captured in the XForms client by
presenting a map widget, having the user trace the line/polygon, and have
the widget calculate and return the corresponding length or area. And to
kick off such a map widget would probably require adding a new appearance
setting to the decimal type to indicate such.
That is all to say, there's existing definitions in the XForms spec to
handle your GPS coordinates, but supporting distance and area too would
require establishing new appearances (IMO). Unfortunately there is no
existing XForms data type that will encompass all three - GPS+distance+area
as a single entity [unlike geopoint which lets you supplement the basic
lat+long with accuracy and elevation data].
Gareth
In my opinion the conversion to the XForm data format is best done on the
ODK side. We could attach hooks like
window.coordinateLogger.getGPSCoordinates();
window.coordinateLogger.getArea();
window.coordinateLogger.getDistance();
to the application itself, which returns a linear array of GPS coordinates
and two numbers, respectively.
Note: I cc Anna Sinelnikova who also is a developer of GEOruler.
/Kristofer Björnson
On Thursday, May 4, 2017 at 7:32:06 AM UTC+12, Kristofer Björnson wrote:
Maybe we can work something out if it is of interest to you. What kind of
data would you like to have? All GPS coordinates of the path, distance,
area?FYI - the existing XForms data types (look here
https://opendatakit.github.io/xforms-spec/#data-types) geotrace (line)
and geoshape (polygon) can take your list of GPS coords. Distance and
area would need to be treated differently in the XForm/by ODK Collect, in
that these would probably map - as distinct values - to the existing basic
data type decimal, whose value would then be captured in the XForms client
by presenting a map widget, having the user trace the line/polygon, and
have the widget calculate and return the corresponding length or area. And
to kick off such a map widget would probably require adding a new
appearance setting to the decimal type to indicate such.That is all to say, there's existing definitions in the XForms spec to
handle your GPS coordinates, but supporting distance and area too would
require establishing new appearances (IMO). Unfortunately there is no
existing XForms data type that will encompass all three - GPS+distance+area
as a single entity [unlike geopoint which lets you supplement the basic
lat+long with accuracy and elevation data].Gareth
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'shape' (closed polygon) by having the first and last GPS coords the same
(ie polygon) or not (ie line)? Not really an issue for getArea() - if
called you can assume polygon and treat whatever GPS coords as representing
a closed circuit. But for getDistance() I'm not sure how you'd determine
whether to return the path length (unclosed) vs perimeter (closed) of the
points...? Having the first and last coords of a polygon be the same would
eliminate any ambiguity.
BTW, there's already the area() function implemented in both Collect and
Enketo. And a distance-between(), I believe. How would the proposed
functionality be different?
Chris
On Thursday, May 4, 2017 at 9:30:16 PM UTC+12, Kristofer Björnson wrote:
In my opinion the conversion to the XForm data format is best done on the
ODK side. We could attach hooks likewindow.coordinateLogger.getGPSCoordinates();
window.coordinateLogger.getArea();
window.coordinateLogger.getDistance();to the application itself, which returns a linear array of GPS
coordinates and two numbers, respectively.Note: I cc Anna Sinelnikova who also is a developer of GEOruler.
Seems reasonsable. Would you distinguish returning a 'path' (line) vs
'shape' (closed polygon) by having the first and last GPS coords the same
(ie polygon) or not (ie line)? Not really an issue for getArea() - if
called you can assume polygon and treat whatever GPS coords as representing
a closed circuit. But for getDistance() I'm not sure how you'd determine
whether to return the path length (unclosed) vs perimeter (closed) of the
points...? Having the first and last coords of a polygon be the same would
eliminate any ambiguity.
- Gareth
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Gareth:
Because the application continuously report the distance and area as it is
being measured, the stored data is on the format that you describe as a
line. The calculation is done such that the result is the area contained by
the shape that results by joining the end point and start point with a
straight line.
Chris:
I have to admit that I am not aware of exactly what capabilities you have
in ODK and it may very well be that you even want to rely on your own
distance and area functions. In particular, this application can only
handle areas small enough that the earths curvature is not significant,
like if measuring a whole continent or so, so if you can do better there is
certainly reason to use your own area calculation function). The reason I'm
reaching out to you is because I was informed a few years back by Eric
Cooper at Afsis that there was interest in incorporatingwhat was then my
android application into ODK and that some students at Stanford was trying
to do so during a Facebook hackathon. With the new website, this should be
much easier. Regarding what functionality that this brings, it is the
possibility to physically trace out paths by walking/driving around the
region of interest.
/Kristofer Björnson
BTW, there's already the area() function implemented in both Collect and
Enketo. And a distance-between(), I believe. How would the proposed
functionality be different?Chris
On Thu, May 4, 2017, 5:42 PM xiphware@gmail.com wrote:
On Thursday, May 4, 2017 at 9:30:16 PM UTC+12, Kristofer Björnson wrote:
In my opinion the conversion to the XForm data format is best done on
the ODK side. We could attach hooks likewindow.coordinateLogger.getGPSCoordinates();
window.coordinateLogger.getArea();
window.coordinateLogger.getDistance();to the application itself, which returns a linear array of GPS
coordinates and two numbers, respectively.Note: I cc Anna Sinelnikova who also is a developer of GEOruler.
Seems reasonsable. Would you distinguish returning a 'path' (line) vs
'shape' (closed polygon) by having the first and last GPS coords the same
(ie polygon) or not (ie line)? Not really an issue for getArea() - if
called you can assume polygon and treat whatever GPS coords as representing
a closed circuit. But for getDistance() I'm not sure how you'd determine
whether to return the path length (unclosed) vs perimeter (closed) of the
points...? Having the first and last coords of a polygon be the same would
eliminate any ambiguity.
- Gareth
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Chris: are the area() and distance-between() you describe XPath functions,
or something else? And do they do compute geodesic (ie curved surface) area
and distance, or just assume flat earth?
cheers,
They're custom functions added to ODK in 2015 or 2016, and I do believe
that they presume flat earth (are generally used for small areas only, like
agricultural plots or maybe, at largest, the borders of refugee camps).
They use pretty standard mathematics for approximation. The area() function
is in XPathFuncExpr.java
XPathFuncExpr.javahttps://github.com/opendatakit/javarosa/blob/82be6fb967da741e4ceb8ba104e4b74767ffdbdf/src/org/javarosa/xpath/expr/XPathFuncExpr.java,
and it looks like distance-between() isn't in there for some reason --
perhaps because we couldn't quickly reach agreement on a suitable name that
the community liked. (However, we have it in SurveyCTO and are happy to
share it anytime.)
Best,
Chris
On Friday, May 5, 2017 at 9:56:10 AM UTC+12, Christopher Robert wrote:
BTW, there's already the area() function implemented in both Collect and
Enketo. And a distance-between(), I believe. How would the proposed
functionality be different?Chris
Chris: are the area() and distance-between() you describe XPath functions,
or something else? And do they do compute geodesic (ie curved surface) area
and distance, or just assume flat earth?cheers,
- Gareth
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Cheers, I assume they'd be used in something like
but I'd love to see a real working form with all the pieces to confirm.
Here is an
example: https://docs.google.com/spreadsheets/d/1oiMpJbqakmdrMUs94vQY6-N83oZj1fuyJYffBMV0Pd0/edit?usp=sharing
Live (temporary
link): https://odk.enke.to/preview?form=http://23.21.114.69/xlsform/downloads/tmp4b2ekddb/area.xml
This seems very compatible with what we have to provide.
/Kristofer Björnson
Here is an example: https://docs.google.com/spreadsheets/d/
1oiMpJbqakmdrMUs94vQY6-N83oZj1fuyJYffBMV0Pd0/edit?usp=sharingLive (temporary link): https://odk.enke.to/preview?form=http://23.21.114.
69/xlsform/downloads/tmp4b2ekddb/area.xmlOn Tuesday, May 9, 2017 at 5:14:35 AM UTC-6, xiph...@gmail.com wrote:
Cheers, I assume they'd be used in something like
but I'd love to see a real working form with all the pieces to confirm.
- Gareth
On Tuesday, May 9, 2017 at 1:13:01 PM UTC+12, Christopher Robert wrote:
They're custom functions added to ODK in 2015 or 2016, and I do believe
that they presume flat earth (are generally used for small areas only, like
agricultural plots or maybe, at largest, the borders of refugee camps).
They use pretty standard mathematics for approximation. The area() function
is in XPathFuncExpr.java, and it looks like distance-between() isn't in
there for some reason -- perhaps because we couldn't quickly reach
agreement on a suitable name that the community liked. (However, we have it
in SurveyCTO and are happy to share it anytime.)Best,
Chris
On Mon, May 8, 2017 at 9:04 PM xiph...@gmail.com wrote:
On Friday, May 5, 2017 at 9:56:10 AM UTC+12, Christopher Robert wrote:
BTW, there's already the area() function implemented in both Collect
and Enketo. And a distance-between(), I believe. How would the proposed
functionality be different?Chris
Chris: are the area() and distance-between() you describe XPath
functions, or something else? And do they do compute geodesic (ie curved
surface) area and distance, or just assume flat earth?cheers,
- Gareth
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Thanks!
Sounds like area() as it exists is adequate and that we should look at
adding distance-between() (or something similar).
I've filed an issue at
https://github.com/opendatakit/xforms-spec/issues/129 so we don't
forget it.
Yaw