[Qgis-user] Did scale change outputting to PDF?

[j.huber at post-ist-da.de]

Hi John,

as I understand it, you created the base map in QGIS. If you use the
measure tool in QGIS to get the distance between two distinct features
in the map (e.g. road intersections) and then measure the same distance
on the printed base map with a ruler, it should be possible to calculate
the scale. Maybe use two distances, one aligned more or less
horizontally and one vertically, to check if the scaling is proportional.

As Andreas pointed out, it is probably a problem with the settings when
the PDF was printed. In my experience it is a good idea to go to print
shops usually working for architects and engineers since they are
familiar with the importance of scaling (for advertising etc. it is more
important that the whole content is printed, so that scaling might be
used to fit the output to the printable area without potential cropping).
You can print directly to a plotter in QGIS if you have access to the
device, avoiding the PDF detour.

EPSG 2264 should be fine. Units should be US feet.

Regards
Jochen


Am 27.05.21 um 07:15 schrieb John Antkowiak:
> Hi. This plan was too simple to fail - but it failed. The charity
> whose project this is needed a large (that is... massive) paper wall
> map on which to plot and rethink its delivery driver assignments. Both
> drivers and delivery addresses are subject to change from week to week
> but it's not a pizza delivery; this is a regular run to supply people
> in a bad way. So the plan was to print the base map (roads and road
> names and county boundaries only) and then print 8.5 x 11 address maps
> with parcel data and orthos. That way, the base maps don't change but
> the physical parcel layer is flexible. (On top of that is a third
> paper layer indicating which drivers go where so someone can stand
> back and take in the whole picture graphically. Not a cutting-edge
> state of the digital art solution, but not everyone is cut out for
> that. It is what it is.) In order for this to work, the parcel maps
> have to be the same scale as the base map. Which they were... in QGIS.
>
> We have to convert all the maps to PDF to print them, and we had to
> send the base map PDFs to FedEx/Kinkos to print the 9 map grid panels
> at 42" by 62" each. 
>
> When we got the big base maps up on the wall, we discovered the scale
> did not match the 8.5" x 11" parcel maps output to PDF and printed
> from home. It's not off by a lot, but it's enough to be painfully
> obvious from a single standard size sheet of paper. I don't know how
> to reverse engineer the big map scale precisely enough to enter a new
> scale number in the QGIS Print Layout. I didn't foresee it because
> this never would've been a conceivable scenario at the engineering
> firm where I picked up my meager GIS skills. (ArcMap sent a map
> directly to the plotter without interim steps.) There was no scale bar
> on the map. It shouldn't have been needed for this.
>
> Did something happen to the map scale when QGIS output the map to PDF?
> Could the size of the image on the pdf page have been adjusted
> manually or otherwise when being sent to a plotter with 42" paper?
> Could the image have been distorted horizontally differently from
> vertically? For the life of me, I cannot trial-and-error guess at a
> scale to enter. I've gone through dozens of new 8.5" x 11" test maps
> trying to guess the correct scale.
>
> Any ideas? 
>
> Thank you all -
>
> John A.
>
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