John,
Is it possible to ask Kinkos what scale they printed the base maps?
They don't have to actually reprint the maps, just go through the
motions. Open the PDF and look at the print options. As Andreas points
out, the default is often "Fit" and there will be a "zoom" or "scale"
percent displayed in the application (I use Foxit, and Adobe and both
show this). The page size parcel maps will have to be printed at this
scale. If they can guarantee that the print scale was 100%, then I
would assume some other export discrepancy.
David
On 5/27/2021 4:15 AM, Andreas Neumann wrote:
Hi John,
No - the PDF export does not distort the scale. But the printing of
the PDF file might.
It is absolutely important that - when printing the PDF - the setting
"Actual size" or "Custom Scale at 100%" is used. All other options
will change the scale.
As far as I know, the default option when printing is "Fit", which
will often shrink the content by some percentage - because some often
"invisible" or white background might be present in the file that
extends right to the edge of the page format. Acrobat then thinks that
the content goes beyond the "printable area" of the printer and will
scale down the whole file.
Hope that clarifies this potential pit-fall when printing PDF files.
It might well be a different issue than the one I describe, but this
is a very common source of error that I know.
Andreas
On 2021-05-27 10:02, John Antkowiak wrote:
Hi, Jochen. Your suggestion sounds do-able; I'll play around with it
and see if I can sort it out. I've got some digital calipers around
here somewhere :)
What I'm hearing is that the process of converting both the base map
(and yes, I did create it in QGIS) and the parcel maps into PDF will
distort the scale. (And that a print shop might compound the problem
by manually fitting the source file to the printable area. Yes?) A
question then is why didn't the PDF conversion distort them all the
same way, to the same degree? The base maps are done now and I
couldn't afford to do them again no matter what, so they are what
they are. Going forward, is there an export option in Print Layout
that will not distort the scale of the parcel maps?
I am so relieved that someone has an explanation for this!
- John A.
----- Forwarded Message -----
*From:* [email protected] <[email protected]>
*To:* "[email protected]" <[email protected]>
*Sent:* Thursday, May 27, 2021, 03:33:12 AM EDT
*Subject:* Re: [Qgis-user] Did scale change outputting to PDF?
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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