3

Beginner alert.

I was given a set of encoded polylines that I need to import into a QGIS project. I understand what encoded polylines are but now I am stuck with how to decode them into some usable formats (I assume csv files?) in order to import into QGIS.

I did some research but have only found resources around encoding the data but not the other way around.

https://developers.google.com/maps/documentation/utilities/polylineutility

^seems to do what I want but I need to download the polylines in a format that can be imported into QGIS.

Here's an example: "_{reFxmjVpAeBn@{@w@aAc@m@yAsBJuAC}BIeAO_Ak@sBCQOg@g@aAk@}@qAwAs@s@}I{JgCqCsC_D}DeEyDgEsA}AwB{BcCwCoGyGqBwByEwFgHqHgDqDkIaJyFuGeEsEeEcEcGkGkEaFyDyDgBqBcAgAm@y@w@gAuCcCmFeHk@i@eAgAaDaDcC_CoBaCeBkCwAiCkCuFoPy]eAkCy@eC{@eDq@kDk@cEwAyQiBsVkAsN}Egn@q@sJ_@iGWgFg@mMcAuWQcCg@yFkBkRc@{EiAmKuBiT]sDWiEy@kPg@_Gg@_E{AuOkAgKo@gFe@oDq@oEe@qBmAeEWkAOaAKoAC}ADiBPeBFc@\wA~@oC@sAh@CVgBJoA@c@EWBkAAcBGgB[yC}AuNu@iHG}B@uBJcBJmAjEeZbAuGz@uFh@}DV]H[RkAfAqGJe@l@mBl@eAv@w@n@]TIj@Ml@In@?Df@n@Fh@@|H|AzDj@zDl@l@F^KhAZhCp@pAXnCr@bBh@nBbAfCdB|@z@vCfDPTjAvAhArAjBjBlBdBlEnC\TCzAtEpCtDtBrEdCdExB~DpBnAj@z@XdAPtBLr@CH?pAQZKfBs@t@e@x@s@|@cAt@mAh@gA@mAlAmEFELSpAyD|A_GfAeC|B}HT_At@gDjCaJZq@dB{F~AeFmCuAgCyAv@mCd@}AfA}C~@oBr@iA|BcDn@gA~@iBTo@~@qCh@gCXoB??P{AP_BU_@e@w@d@v@nArBl@v@ClBlBtAdATnAXLCFAXiALc@Ng@X}A^eCvB{T\qDZsBSeATmBr@mE?@ASVkAv@iDlBqHvA_FhAcDv@qBtBaFbIyQpBsDrAoBdAiAp@k@r@g@v@a@lAi@dBk@dG{AfD}@v@YzAq@|BsAfA{@[|A_BvAiBv@oAAiB@A@cAf@_BzBaJrM}j@x@eCz@mBbAgBlAeBhAmArAmAhCkB|MeJnD_CjByAxE}DtG{FlNsL~WaUjMmK|GyFjR}OdI_HhYcV~SoQfCwBnGeF~I}HbHcGnDyCDmCbJyHhA}@~FeF~GwFnNmLzCkCtJkJ|MeNDeDjGkGxGmGtAyApHcHrBiBlAsAdF_GRyZhI{MlJcPBeC~PaYdPaXjOqVbLcRdXmc@dDqFhLgRtGmKj@aAlB}Cz@oAR]tAeC~EqHtWwb@fRc[bDgGzB}Df@{@fIuLxGsKzBwCtCyCbB{AfAw@bC}AlGgDbEsBdIgEl@]fNkH~VcN~f@wWzP_Jr@c@zIeFAo@xEwCbHmEdGyDnIsF~MyIrJmGrUaOlSmMzDgC~k@e@bf@{Z~n@ca@|QqLtRcMdp@ab@naAkn@fBeADaBfDwANBJ?nAWhCm@^Gf@@XHZPp@f@xDfCpF}NpAcDpA_DjF}MtGyPLY]UyDkCoFqDaAC_@z@aApBoAzC]W??\Vt@iBd@gAdAuBNa@r@gBz@h@~B~AdBhAhChBZTLYnCeHtAmDnHgRjHcRtCqH~FcOvBuFdEyKpLoZvL_[v@mBjH}QXaAfAkCx@sBXaAlEwKpA}CfDgIx@mB^y@FE@Ap@uAfCaGrIsSA_CxAeDnGyOlFiMdBeECcGhG_O??AaCnDrC~DvCrNtKz_@~YfUfQtFhE~DD|@p@\Pn@RbATjBBpABzANv@ThAh@|@n@@^ZXf@p@NfA@t@KXSV_@LWA[KU]Ie@?WJk@Le@hA}CBK@g@bAwBlCkGzFoN~KqYpOk@zF_OzAaDfB_DpCmEzJwMfPqTT}XjLoOvJwMh@q@vK}NjEwFbDsErKiOvWi_@d\{d@V_@r@cA~@qAb@u@xB{CrIyLhIoLxKsOnG_JjB}Bp@u@fC_CxCyBnC{A|D}AfFuBrOeGG}Bfh@mShc@}PdIeDhG{BbE{AjD_AzDw@pFq@zJiA|@MxAKbNcBfJaAtOkBbKiA~TwCzFo@nC]bKaAhGm@~Hi@d@AbPaA~AOpCe@pEkAdA]zEkBj@UfB}@|Aw@xBs@|Ac@xJ_Cf@Dr@GrBa@fBYdBQvDQv@MlA]pG{BrAc@xCu@~Cm@zCg@|@WSqAOeA_@oDMqDT}`@JaC^qBZcAZw@xD}HvAsCpBiE~BkGJYg@c@eCaBO^i@tAc@dAo@~A"

Which lead my other question: most of the examples I found online were definitely not as long as the above. is there something wrong with it?

  • An example of what you have would be great. If the file is text (CSV, XML, GML, KML etc) a few lines would show how they are encoded. Without this information we would only be guessing. – Michael Stimson May 17 '16 at 23:48
  • Sorry for neglecting to include examples. I have made the edits above! – zero4case May 18 '16 at 4:58
2

There's some python code to do it here:

https://gist.github.com/signed0/2031157

You've not told us you have any python skills, but the way this works is to take a string and return a list of coordinate pairs:

>>> import gistfile
>>> gistfile1.decode("_{reFxmjVpAeBn@{@w@aAc@m@yAsBJ  .... etc... ")

which returns:

[(-3.82701, 37.78496), (-3.8265, 37.78455), 
 (-3.8262, 37.78431), (-3.82587, 37.78459),
  (-3.82564, 37.78477) .... etc ....

I'm not certain if that's lat-long or long-lat - if you know where you expect the points then you can tell.

Discovering it is so simple made me think I should write a QGIS plugin for it. The only related thing I could find is one that writes these formats from existing geometry:

https://github.com/pvinton/QGIS-EncodedPolylineExporter-plugin

so probably doesn't help you. You want an importer...

So I hacked one together, in javascript, from parts. This web page will convert a file containing that gobble-de-gook encoding string into a link to a GeoJSON file that will load into QGIS:

http://barryrowlingson.github.io/polyline-to-geojson/

  • Thank you for your help! No, I am super new to coding/CS so no skills in python or JS or any CS languages. I used your tool and was able to generate a geojson file for the encoded polyline I included above. I imported the file on geojson.io and got a straight line. What did I do wrong? – zero4case May 18 '16 at 18:22
  • Try the web converter again - I've changed the geoJSON format and now I can load it into QGIS. Its a wiggly line roughly diagonal across. – Spacedman May 18 '16 at 20:30
  • Thanks for getting back to me! I actually just posted another follow-up question to this here: gis.stackexchange.com/questions/194093/… But let me try the converter again!! – zero4case May 18 '16 at 20:37
  • I think I didn't flip the coordinates when I should have. If you can give us a sample string and tell us where it should go I'll make sure I get it the right way round. – Spacedman May 18 '16 at 21:20
-4

Looks like there's quite a few options for you on Google

We're looking for long answers that provide some explanation and context. Don't just give a one-line answer; explain why your answer is right, ideally with citations. Answers that don't include explanations may be removed.

  • 1
    google search links as answers are discouraged. – Spacedman May 18 '16 at 7:42

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