Category: Mapping

Layer symbology for NHD data

By Charlie Frye, Esri Chief Cartographer

NHD - Thumbnail

Most maps should have some depiction of hydrography.  The problem is, if you’re not familiar with the data or the typical symbology conventions, it’s hard to find the time to make the required effort. In the U.S., hydrography data is available from the USGS in the form of the National Hydrography Dataset (NHD). Once you download the NHD data you need (TIP:  you need to allow popups on this site), the next task is symbolizing it. To help with that here are a few layer files that you can load into ArcMap, then use the Layer Properities’ Source tab to change the data source to your data.

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Bad maps are bad for business

By Charlie Frye, Esri Chief Cartographer

Bad maps, unlike bad press, do not garner the sort of attention that can be capitalized upon. Bad maps are strong impediments to gaining mind share, and represent a significant risk to depleting mind share. Why? Bad maps are a visual, i.e., strong, communication method and convey incompetence and poor judgment.

To many of us this is obvious, but we consistently hear from people who are professionals who have to make maps.  Though most would not describe themselves as cartographers or mappers, they want us to help them make a case for better cartography in their organizations. Continue reading

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Automation tip for Python-based field calculations

By Charlie Frye, Esri Chief Cartographer

I do most of my data automation in Python–I’m no expert with Python, but I learned the basics a few years ago and that’s served me well. One of the tasks I frequently use Python for is automating the management of attributes, i.e., adding, deleting, and calculating fields.  Continue reading

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Making maps with unfit data

By Charlie Frye, Esri Chief Cartographer

Occasionally I’m asked to come into a project to introduce some cartographic thinking into work that ordinarily might not have much. I spent most of last week with some folks who know water utility GIS. I helped by designing a status map, and took some of that work to make some improvements to an editing map and a mobile map. The status map needed to be a multi-scale base map that showed the water network data (mains, valves, meters, etc.), and the status of assets and water service.  Many different people within a water department, local government, or even the public might see the map. This map had to be functional, attractive, and free of obvious  errors and awkward symbol or labeling choices.

The main issue I faced was one of unfit data.  This made the task of producing an attractive and functional map quite a challenge. The quality of the geometry of the street centerlines was not so good-streets strayed over parcel boundaries and curb lines. At small scales this data looked like it had been produced in less than five minutes by a decidedly unskilled draftsman. At large scales the data was useless; street labels needed to be on the streets (not on parcel lines or water mains).

That is a showstopper. Unfit data will never work to make a good map.  It’s a fact.

My colleagues on this project, beyond being very good at their jobs, were undeterred realists.  They knew the data wasn’t perfect; it’s all we had. In their view it was more important to get our work done than to fret over not having a beautiful map. Further, if I, the cartographer, couldn’t fix it, then that was an even better excuse than any of them not being able to fix it.

Instead of arguing that cartography is the answer and can fix everything, I listened. I heard how most water departments don’t make their own street centerline data; they get most of their base map data from other departments or their county. They have no budget to fix the data. It’s a frustrating story, and one I’ve heard too many times over the past dozen plus years.

I’ve come to understand this is a problem of organizational culture.  Here’s why:

  • Having to make maps with unfit data isn’t fun and erodes the motivation of the people making the maps. If you know you’re going to make a poor map because of circumstances beyond your control, you may learn to merely be happy with your paycheck rather than your job.
  • Produce less than stellar maps on a consistent basis and there is a danger of getting a reputation for not being brilliant, or worse, incompetent.
  • Business cycles, political winds, or pointy-haired bosses; it doesn’t really matter why, but eventually organizations seek to rid themselves of incompetence or their less than brilliant workers. But since water departments (and others) need maps an inward focus often results:  “We don’t have to show the other departments our maps…” becomes the mantra.
  • Inwardly focused departments equate to interdepartmental dysfunction. Did you ever wonder why the water department doesn’t know about the street department’s repaving projects?

So, that’s somewhat tongue-in-cheek, but I bet some parts hit close to home. What should be done about this?  Experience has shown me that most local government departments have shared requirements with other departments. But I don’t hear many stories about how the map makers in the water department called the planning department with their requirements for street centerlines and maybe hint that resources could be shared to get the job done.  The job needs to get done-there is no excuse for a bad map to be produced in a professional setting. There is nothing professional about a bad map.

Good looking maps convey a sense of competence, create trust, and are the basis for confidence.  Show me an organization that doesn’t want those things. Google and Microsoft have proved good looking maps are valuable.  Sure the data in those maps isn’t quite perfect, but if it’s presented sufficiently well, people clearly don’t mind using it.

Infrastructure mapping doesn’t have to be ugly or be bound by a Rapidograph pen and CAD legacy.

Maps Unfit - Figure 1

Too many water department maps look like this

Maps Unfit - Figure 2

The original water department maps could look more like the modified version by taking advantage of concepts like visual hierarchy and applying standards for legibility.

One last bit of wisdom gained was in presenting our project, we saw that just having the well designed map at the core of what we were doing made a huge positive difference. A little sadly, from my perspective, nobody cared how it got made. C’est la vie.

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The state of data frames in layout view

By David Barnes, Esri Product Engineer

From time to time I hear from users or see postings indicating that they find the various states data frames can have a bit confusing.

Data frames on the layout can be active, selected, focused or some combination (or none) of the above.

There is always one active data frame. The active data frame tells ArcMap to use this data frame as the reference when inserting map surrounds, Continue reading

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How to symbolize topo lines

Question: I’m trying to come up with a straightforward way to symbolize topographic contours from a polyline featureclass. For example, I would like to be able to make multiples of 250 darker lines than the others. Ideally I would like to do this without having to add columns to the featureclasses, and without having to manually specify each contour interval that I want to be dark.

I thought perhaps I could write a definition query that would select multiples of 250, but I have had no luck finding a function that returns a remainder or something along those lines.


Answer: Add a short integer field to the contours data.  Calculate that field using an Advanced field calculator statement, like:

k = 0
if [Contour] MOD 250 = 0 then
k = 1

Set the result to = k.

Using a definition query will slow drawing performance to an unacceptable level.

Formerly a Mapping Center Ask a Cartographer  Q & A.


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Hillshades for analysis maps

By Charlie Frye, Esri Chief Cartographer

Hillshades for Analysis Maps Thumbnail

It is often useful to use a hillshade raster to show terrain to support other information in a map such as an analytical surface like population density, or a thematic overlay like soils. There is one significant problem with this; however, which is that the shading from the hillshade modifies the colors of the main information layer making them artificially dark or washed out. That makes map reading and applying what you learn from a legend a frustrating task.

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Restricted color ramp

By Aileen Buckley, Mapping Center Lead


We recently got a question on Ask a Cartographer that related to the use of a restricted color ramp. The person asked, “Is there an easy way that I can make all the counties in one state variations on one hue, but each state a different colour so that the map readers can easily distinguish between states and counties?” The solution is a restricted color ramp and it can be used in many different situations. Continue reading

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Text: Size definitely matters

By Charlie Frye, Esri Chief Cartographer

I don’t hear this so much from cartographers and GIS professionals as I do from nearly everybody else who has to read our maps, “I didn’t even read the text on the map’. Matt Baker’s recent post addresses one of the most common causes, overly wide paragraphs, and I’ll cover another here, which is the size of text.

A paragraph of text on a map has a tendency to look like a block of graphical noise if the type size is too small. Continue reading

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Cropping a map

Question: I downloaded a map from the Internet and stored it as a .jpg file, but I only need one specific part on the map to print. I tried looking for some way to crop the map but I can’t find one in ArcMap. I tried to crop it first in Paint, but the picture is blurry when I try to magnify it in ArcMap. How do I fix this issue?

Answer: To crop an image in ArcMap you will need to:

  1. Add the image as raster data, making it a layer.
  2. Zoom to the extent you want to crop–resize the ArcMap window if needed.
  3. Right-click on the layer and choose Data –> Export.
  4. In the upper left, change the extent to Data Frame (meaning the current extent).
  5. Set the other export properties and save the cropped image.

Generally speaking the concept of raster data in GIS is agnostic to the meaning of the pixel values, as individuals or as a collective.  This differs from the graphics community which usually assumes you have an image of something, and the most common metaphor is a photo, hence the term “crop”.  The GIS synonym is “clip”.  So there is a Clip tool for Raster data.  If you’ve got lots of images to clip, then that tool is the basis for automation.

Formerly a Mapping Center Ask a Cartographer  Q & A.

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