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GIS / Mapping Working Group
The Geographic Information Systems (GIS) / Mapping working group is a network of CUNY students, faculty and staff who are interested in sharing methods and techniques, and finding support from others about ways GIS can be used to further research and teaching.
The GIS/Mapping working group is part of a GC Digital Initiatives program designed to create collaborative communities of Digital Fellows, CUNY-wide graduate students, staff, and faculty to meet regularly and share their areas of interest. The working groups provide a sustained, supportive environment to learn new skills, share familiar skills, and collaborate with both the Digital Fellows and the CUNY digital community.
If you are using Geographic Information Systems or other mapping technologies in your teaching and/or research, or if you are interested in mapping your data, or using GIS technology to analyze/visualize your data, we invite you to join the GIS/Mapping working group.
Peruse our mapping resource bank here: https://commons.gc.cuny.edu/groups/gis-working-group/docs/gis-mapping-resources/
For the Spring 2024 semester, the GIS/Mapping working group will meet in the Digital Scholarship Lab, Room 7414, every other Tuesday from 2-4 p.m. Check out our event calendar for the specific meeting dates. Please stop by!
Admins:
Top Mapping Mistakes
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Posted by Olivia Ildefonso (she/her) on April 21, 2021 at 10:49 amHi all,
I’m writing an article now that I hope will be helpful for mapping beginners. It’s about the top mistakes that folks make when they are first learning GIS. Are there any that come to mind for you that you remember from your mapping journey or from teaching others? It would be things like forgetting to make sure the field types match when you are doing a spatial join. Any examples that come to mind for you?
Thanks so much!
Olivia
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One of my pet peeves is novice GIS-ers making choropleth maps to display absolute numbers (counts), rather than rates, percentages, proportions, per capitas, medians, or averages, etc. Another problem people often get into is relying on default options in GIS software packages, without really thinking about what they are doing and whether or not in the specific analysis or map they are working on makes sense with the defaults.
Using bi-chromatic color ramps to symbolize a low to high continuum, instead of single color in graduated hues. The bi-chromatic color ramps should really be used only for situations where a classification range goes above and below a standard deviation mid-point, or a threshold value, for instance. Even worse is when people use a multi-colored circus jumble ramp for quantitative data, which negates the intuitive purpose of a single color ramp with gradation, letting the map viewer understand at a glance without much reference to the legend, what the colors on the map indicate.
I realize that all of these are more or less cartographic issues, not GIS specifically, but because GIS now allows map making almost indiscriminately, it’s important to understand all the ways that maps can be cartographically inaccurate and misleading if one isn’t well-versed in standard cartographic best practices. Some very incorrect maps can be produced which have all the appearances of a professionally created map.Juliana Maantay, Ph.D., M.U.P., F.R.G.S.
Professor of Urban Environmental Geography
Director: Geographic Information Science (GISc) Program;
MS-GISc Program; and the Urban GISc Lab
NOAA-CREST Research Scientist
Department of Earth, Environmental, and Geospatial Sciences
Lehman College, City University of New York
250 Bedford Park Blvd. West
Bronx, NY 10468
TEL: (718) 960-8574; FAX: (718) 960-8584
juliana.maantay@lehman.cuny.edu
Faculty Profile: http://www.lehman.edu/academics/eggs/fac-maantay.php(https://mail.lehman.edu/owa/redir.aspx?C=JyvINcu5vqHrfPIz4NvBpSPK-oFcbs1Ep7J2CAaJl7JtUdYs4oXVCA..&URL=http%3a%2f%2fwww.lehman.edu%2facademics%2feggs%2ffac-maantay.php)“Geography, sir, is ruinous in its effects on the lower classes. Reading, writing, and arithmetic are comparatively safe, but geography invariably leads to revolution.” (1879 testimony before a Select Committee of the House of Commons, London, England, regarding expenditures of the London School Board)
“The scientist is not a person who gives the right answers, [s]he’s one who asks the right questions.” (Claude Lévi-Strauss, 1964, Le Cru et le Cuit [The Raw and the Cooked])
“Those who plan do better than those who do not plan, even though they rarely stick to their plan.” Winston Churchill
“Be sure that no good may be expected of anyone who is satisfied with what he knows. To investigate is the task of the knowledgeable.” (Book of the Sea, 1513, by Piri Re’is, Ottoman cartographer, geographer, and navigator to Suleiman I)
Juliana raises some very important points. I would just add that people new to map-making need to remember that it’s “choropleth” not “chLoropleth”! (A common and annoying mistake!)
Also, even though the book is a bit dated, everyone in this field should read Monmonier’s “How to Lie with Maps”, because it explains so clearly and effectively why you shouldn’t make the kinds of mistakes that Juliana notes below.
Steve
=======================================
Steven Romalewski
Director, CUNY Mapping Service
Center for Urban Research at The Graduate Center / CUNY
365 Fifth Ave., Room 6202
New York, NY 10016
TEMPORARY PHONE: 917-975-3794
Office phone: 212-817-2033
sromalewski@gc.cuny.edu<mailto:sromalewski@gc.cuny.edu>
http://www.urbanresearch.org(http://www.urbanresearch.org&d=DwMFAg&c=8v77JlHZOYsReeOxyYXDU39VUUzHxyfBUh7fw)
http://www.gc.cuny.edu/urbanresearchmaps
@SR_spatial
=======================================From: Juliana Maantay (GIS / Mapping Working Group) <noreply@gc.cuny.edu>
Sent: Wednesday, April 21, 2021 1:54 PM
To: Romalewski, Steven <SRomalewski@gc.cuny.edu>
Subject: Re: Top Mapping MistakesI am a recent learner, and here are a few things that I find challenging:
- GIS-specific software (such as QGIS) is great, but there are so many package features and several ways to access these capabilities, some of which can be somewhat redundant. Figuring out how to do any one specific thing – even the simplest things – can be a fairly tedious exercise in trial and error. If you are working in GIS software, definitely make careful notes for yourself from the very beginning, so that you can replicate what you did or retrace your steps if you need to troubleshoot later. It’s a huge headache to get several steps into a mapping project and then realize you made a mistake somewhere but can’t remember the exact steps/assumptions/settings you used along the way.
- Be prepared to redo everything from the beginning at least three times.
- A lot of choropleth maps kind of tell the same story. Even when values are normalized in some way, it often looks like the map title could be “Where are the people?”. So one trick I use is to just make sure my choropleth map isn’t trivial in that way; if that generic title could apply, then I think about whether I am showing the right variables in the right way.
- I totally agree with Prof Maantay’s point about bi-chromatic color ramps! These can be very powerful tools for visualizing difference relative to some intermediate value, but shouldn’t be used arbitrarily to add visual interest/appeal to a map.
- I was so excited to make maps that made sense, I wanted to include tons of details. But they get messy really fast. When in doubt, try leaving it out. Think Tufte. Every choice you make should be part of your story.
- Learning mapping visualization is really forcing me to think deeply about the way visualizations are organized in “layers”. If you are familiar with R and ggplot, this may make sense. If you are not familiar with the concept of visualization layers, definitely pay attention to how maps are done in layers, and think about how this generalizes to other visualizations.
It’s great to hear that you like Monmonier’s _How to Lie with Maps_, Steve,
as I teach it every year in my intro to digital humanities course!Matthew – Another oldie but goodie along similar lines is the book “Mapping: Ways of Representing the World,” by Danny Dorling (of cartogram fame) and Dave Fairbairn, from about 1997. Not sure if it is still in print, but it’s a slim little book that does a great job of explaining some of these issues, and a nice overview of the art and science of mapping.
Juliana Maantay, Ph.D., M.U.P., F.R.G.S.
Professor of Urban Environmental Geography
Director: Geographic Information Science (GISc) Program;
MS-GISc Program; and the Urban GISc Lab
NOAA-CREST Research Scientist
Department of Earth, Environmental, and Geospatial Sciences
Lehman College, City University of New York
250 Bedford Park Blvd. West
Bronx, NY 10468
TEL: (718) 960-8574; FAX: (718) 960-8584
juliana.maantay@lehman.cuny.edu
Faculty Profile: http://www.lehman.edu/academics/eggs/fac-maantay.php(https://mail.lehman.edu/owa/redir.aspx?C=JyvINcu5vqHrfPIz4NvBpSPK-oFcbs1Ep7J2CAaJl7JtUdYs4oXVCA..&URL=http%3a%2f%2fwww.lehman.edu%2facademics%2feggs%2ffac-maantay.php)“Geography, sir, is ruinous in its effects on the lower classes. Reading, writing, and arithmetic are comparatively safe, but geography invariably leads to revolution.” (1879 testimony before a Select Committee of the House of Commons, London, England, regarding expenditures of the London School Board)
“The scientist is not a person who gives the right answers, [s]he’s one who asks the right questions.” (Claude Lévi-Strauss, 1964, Le Cru et le Cuit [The Raw and the Cooked])
“Those who plan do better than those who do not plan, even though they rarely stick to their plan.” Winston Churchill
“Be sure that no good may be expected of anyone who is satisfied with what he knows. To investigate is the task of the knowledgeable.” (Book of the Sea, 1513, by Piri Re’is, Ottoman cartographer, geographer, and navigator to Suleiman I)
There are many great comments here!
Here are a few other contributions, though I’m not sure if they pertain
specifically to beginners:– Although they are still the most widely distributed GIS format, take
into account the limitations of shapefiles, such as:
– The limit of 10-character-length for attribute names. This can be
particularly problematic after a spatial join in which you kept the join
layer filename as a prefix in the new dataset… once you save it as a
shapefile, attribute names might all turn into EXAMPLE~1,
EXAMPLE~2… and
so on, making it impossible to know what each attribute is.
– That you need to keep all files that come with your .shp together
in the same folder and with the same filename, especially the
.shx and the
.dbf, which are mandatory files to keep.
– Related to the previous one, that spatial index files (.sbn, .sbx)
can sometimes corrupt the spatial representation of the layer and affect
any geospatial analyses you run on the layer. To solve this issue, just
delete those files. This has happened to me with MapPLUTO layers on
QGIS, and I am not sure whether this is an issue in other
software or with
other data.
– For the reasons above, consider using other file formats, such as
Geopackage, Spatialite, Geojson, though each of these may have their own
pros and cons, the biggest con likely being limited/no compatibility with
certain GIS software such as ArcGIS.
– And here are some newbie issues that you could run into when using CSV
files:
– Be careful if you edit a CSV dataset with Excel prior to importing
to your GIS software, as Excel might automatically change long
numbers into
scientific notation. Once you save the CSV, those long numbers will be
truncated. This is particularly problematic for US Census numeric ID
numbers. Excel is also known for messing up date fields of CSV files.
– If the software keeps misinterpreting an attribute type (e.g.,
reads an ID as an integer instead of a string), and this limits your
ability to join data to a layer, you can create a .csvt file
with the same
name and folder as the .csv file, in which you can specify the data type
for each column in your dataset. For example: a .csvt which
contains solely
the text:* “String”, “Integer”, “Real”, “Date”, “Time”, “DateTime”*,
will automatically interpret the first data column as a string,
the second
column as an integer, and so on, and will be opened as such by
Excel, QGIS
and many other CSV-reading apps.Hope this helps!
Best,
Javier
—Thanks Olivia for starting this great discussion!
A few thoughts:
– Not setting up the “environmental settings”, particularly when working with raster data. The “mask” , “cell size”, and “snapping to” settings can make it or break it.
Also, env. settings can be set at the general level and tool level. I recommend to always double check before running any tool.– This is not specific to GIS, but “being too enthusiastic” to start the analysis without cleaning the data first is obviously an issue, as well as
using one output to as the next input without keeping track of what you are doing and most importantly, without checking that the result is as expected.-Long path names or file names containing special characters or that are not meaningful (e.g. temp3).
-Not having a proper file management structure can lead to many headaches as the number of files can grow very quickly.
– Following up with Juliana on the defaults, the same applies to the tools and modules. Assuming that the default parameters for a tool
are appropriate for all data types or analyses can be very problematic.– In response to Javier regarding the field limitations of shp. I would add the geodatabase format to your list of suggested formats, it is proprietary
and there is still a limit of 64 characters for the file geodatabases, but it is usually enough. I insist on using ArcCatalog for file management to keep the files together in every course I teach with ArcGIS. .– A few cartographic issues: 1) the first maps of some students include scale bars and north arrows that are too big and/or too ornamented, which often clashes
with the style and/or its purpose. Along the same lines, I have noticed the use of effects in the background or colors that are distracting.
2) using decimal degrees on a scale bar, it is rare, but definitely has an impact when seen and not a good one.I am not sure if this is what you are looking for, happy to talk more.
Best,
EliaThanks Olivia for starting this great discussion!
A few thoughts:
– Not setting up the “environmental settings”, particularly when working with raster data. The “mask” , “cell size”, and “snapping to” settings can make it or break it.
Also, env. settings can be set at the general level and tool level. I recommend to always double check before running any tool.– This is not specific to GIS, but “being too enthusiastic” to start the analysis without cleaning the data first is obviously an issue, as well as
using one output to as the next input without keeping track of what you are doing and most importantly, without checking that the result is as expected.-Long path names or file names containing special characters or that are not meaningful (e.g. temp3).
-Not having a proper file management structure can lead to many headaches as the number of files can grow very quickly.
– Following up with Juliana on the defaults, the same applies to the tools and modules. Assuming that the default parameters for a tool
are appropriate for all data types or analyses can be very problematic.– In response to Javier regarding the field limitations of shp. I would add the geodatabase format to your list of suggested formats, it is proprietary
and there is still a limit of 64 characters for the file geodatabases, but it is usually enough. I insist on using ArcCatalog for file management to keep the files together in every course I teach with ArcGIS. .– A few cartographic issues: 1) the first maps of some students include scale bars and north arrows that are too big and/or too ornated, which often clashes
with the style of the map. Along the same lines, I have noticed the use of effects in the background or colors that are distracting.
2) using decimal degrees on a scale bar, it is rare, but definitely has an impact when seen and not a good one.I am not sure if this is what you are looking for, happy to talk more.
Best,
Elia~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Elia Axinia Machado
Associate Professor
Earth, Environmental, and Geospatial Sciences,
Lehman College, City University of New York
Office: Gillet Hall, room 323
Tel:718-960-1103 – Fax: 718-960-8584Thank you so much to everyone who contributed to this discussion! Your insights were super helpful. Here the article that I wrote that incorporates a lot of your feedback: Top Mapping Mistakes
Excellent synopsis! I will share it with my students. Thanks. JAM
Juliana Maantay, Ph.D., M.U.P., F.R.G.S.
Professor of Urban Environmental Geography
Director: Geographic Information Science (GISc) Program;
MS-GISc Program; and the Urban GISc Lab
NOAA-CREST Research Scientist
Department of Earth, Environmental, and Geospatial Sciences
Lehman College, City University of New York
250 Bedford Park Blvd. West
Bronx, NY 10468
TEL: (718) 960-8574; FAX: (718) 960-8584
juliana.maantay@lehman.cuny.edu
Faculty Profile: https://www.lehman.edu/academics/eggs/fac-maantay.php
Urban GISc Lab Research Work: https://www.lehman.edu/academics/eggs/maantay-research.php“Geography, sir, is ruinous in its effects on the lower classes. Reading, writing, and arithmetic are comparatively safe, but geography invariably leads to revolution.” (1879 testimony before a Select Committee of the House of Commons, London, England, regarding expenditures of the London School Board)
“The scientist is not a person who gives the right answers, [s]he’s one who asks the right questions.” (Claude Lévi-Strauss, 1964, Le Cru et le Cuit [The Raw and the Cooked])
“Those who plan do better than those who do not plan, even though they rarely stick to their plan.” Winston Churchill
“Be sure that no good may be expected of anyone who is satisfied with what he knows. To investigate is the task of the knowledgeable.” (Book of the Sea, 1513, by Piri Re’is, Ottoman cartographer, geographer, and navigator to Suleiman I)
Olivia, this is a great overview. Helpful article!
=======================================
Steven Romalewski
Director, CUNY Mapping Service
Center for Urban Research at The Graduate Center / CUNY
[CUNY-GC-logo_whitetextblueback60hi]
365 Fifth Ave., Room 6202
New York, NY 10016
Phone: 212-817-2033
sromalewski@gc.cuny.edu<mailto:sromalewski@gc.cuny.edu>
http://www.urbanresearch.org(http://www.urbanresearch.org)
http://www.gc.cuny.edu/urbanresearchmaps
@SR_spatial
=======================================From: Olivia Ildefonso (GIS / Mapping Working Group) <noreply@gc.cuny.edu>
Sent: Wednesday, May 12, 2021 10:41 AM
To: Romalewski, Steven <SRomalewski@gc.cuny.edu>
Subject: Re: Top Mapping MistakesThanks for sharing Olivia! great article.
Best,
Elia~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Elia Axinia Machado
Associate Professor
Earth, Environmental, and Geospatial Sciences,
Lehman College, City University of New York
Office: Gillet Hall, room 323
Tel:718-960-1103 – Fax: 718-960-8584
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