informed decisions

informed decisions

In a previous post, we listed five reasons to develop your own municipal GIS data: control, breadth, depth, flexibility, and presentation. Taken together, the tangible outcome should be making more informed decisions.

informed decisions

To further illustrate this issue, let’s take a look at a side-by-side comparison. The image on the left is a map developed as a working document by one of our clients using manual methods prior to our involvement with their project. It shows part of a block where they wanted to explore targeted property acquisition. The questions they wanted to answer were: should we pursue acquiring properties on this block, which ones, how much will it cost?

In contrast, the image on the right shows a map of the same area developed by our staff in approximately 15 minutes.

The map on the right leverages the power of geospatial data and geographic information systems to do the following four things:

Communicate more completely, using “higher density” data

The GIS map communicates much more information at one time. Both maps show parcel lines and owner names. However the second map additionally illustrates building locations, neighborhood context, occupancy, and land use.

Save time in developing and repurposing graphics

While it looks fairly simple, the map on the left represents several hours of work involving tax map and deed requests to various City and County offices just to label the properties with owner names. Our client also took time to visit the neighborhood to obtain current occupancy information. This is the way things were done before the advent of municipal GIS in the client’s City.

We were able to accomplish the same task much more quickly and completely through the use of GIS data and didn’t have to leave our offices to get the job done.

The first map has additional drawbacks because it is analog. Making a paper original larger or smaller for use as a poster or on web pages is difficult and won’t look very good. The second map is infinitely scalable, editable, and can be forwarded to anyone as a PDF within seconds.

Focus discussion via filtering

The second map allows you to keep discussion on track because we suppressed labels on parcels that were determined to be irrelevant to  discussions. Additionally the use of bright colors to highlight certain parcels naturally directs the eye and develops interest in them.

Recognize and share patterns more easily

By using colors rather than text, the GIS map graphic is legible from a distance. With a cursory glance, the pattern of vacant buildings compared to empty lots is easily recognized.

But our comparative case study doesn’t end there, after implementing a comprehensive municipal GIS our client was able to dig deeper for authoritative details. Just under the surface of the GIS map is a wealth of data linked to each parcel from the County tax assessor’s office. The client can click on any of the parcels to instantly obtain assessment and property sale data like that found in the table below. This type of operational intelligence allows for more informed decisions to be made for the project area and the City.

informed decisions

informed decisions

Geospatial Data layers

Developing an edge of pavement layer

A small scale map of your community shows the relationship of streets by using a single line that represents where the approximate center of the road is located. That’s great when the map is “zoomed out” to show the entire municipality. When someone “zooms in” on the map to a neighborhood, you should show them more detail such as the width of the paved roadway.

In our last blog post, we demonstrated how you can download lots of useful information from PASDA to build a simple base map as the starting point for a municipal GIS. In this post we’re going one step further to give our map an “edge of pavement” layer that shows the location of the road surface.

Some benefits of an edge of pavement (EOP) layer include allowing people to easily recognize the difference between narrow alleyways and major city streets. It facilitates take-offs for repaving or construction work. It also eases analysis of turning movements for emergency apparatus.

Since an EOP is made up of polygon features which can be used to calculate area in square feet or acres, it is also the starting point for mapping impervious surfaces in your municipality for stormwater management purposes.

The broad steps in this process are:

  1. Find and download the LIDAR breaklines tiles for your location
  2. Filter the breaklines tiles to show only roadways
  3. Combine all of the breakline tiles into a single continuous layer
  4. Edit the breaklines to prepare them for polygon conversion
  5. Convert the breaklines to polygons
  6. Edit the polygon feature to remove areas that are not paved.

To get detailed instructions on how to complete the process using ESRI ArcGIS for Desktop Advanced, fill out the form below.

Request edge of pavement instructions

Geospatial Data layers

free data

free data

In our last  blog post we talked about 33 feature classes you can map in your community without using a GPS. A key element for mapping new data is that you must have a base map (including aerial photography) to serve as a backdrop for your municipal GIS. If your Pennsylvania community hasn’t yet developed a base map, now is the time to start with some easily obtained (and free) data from Pennsylvania Spatial Data Access (PASDA). PASDA is the definitive source for open source geospatial data in Pennsylvania. PASDA in a one-stop data portal that aggregates data from 63 data providers including: local, county, state and federal governments, educational institutions, and non-profit organizations.   The data sets from PennDOT, PA DEP, PA DOH, and PA DCNR are updated regularly. If you haven’t visited, you definitely should take a look to explore the depth and breadth of the information available.

A very useful feature of the PASDA website is the Pennsylvania Imagery Navigator ( ).   The Imagery Navigator allows you to zoom to any part of the state and download all of the imagery for that location. The imagery published through this search interface includes: USGS quadrangle maps, digital elevation models, LiDAR point clouds, contours and breaklines, USDA annual imagery, PAMAP orthophotography, as well as selected regional and county orthophotography.

Simple Base Map Demonstration

Using the “Data Shortcuts” menu on the right side of the PASDA home page, you can acquire the data to assemble a very serviceable base map. To prove this point, starting from scratch, we assembled a simple base map that shows the following data: state and local roads, county and municipal boundaries, railroads, public lands (parks, forests, game lands), waterways, flood hazard areas, 2015 aerial photography, wetlands, soils, and elevation contours. It took us about 90 minutes to download all of the data and compile it into an ArcGIS map. The result of the project is shown in the following four screen shots.

Of special interest to municipalities just starting on the geospatial journey, the last map includes road edges derived from PAMAP LiDAR data. Our next blog post will demonstrate how you can complete that process on your own.





More About PASDA


Pennsylvania Spatial Data Access (PASDA) is Pennsylvania’s official public access geospatial information clearinghouse. PASDA was developed in 1996 by the Pennsylvania State University.

PASDA is a cooperative project of the Governor’s Office of Administration,  Office for Information Technology, and  Penn State Institutes of Energy and the Environment  of the  Pennsylvania State University. Funding and support is provided by the Pennsylvania Office for Information Technology. Penn State contributions include system administration support and infrastructure from the  Institute for CyberScience, and the  College of Earth and Mineral Sciences.

PASDA was developed as a service to the citizens of the Commonwealth of Pennsylvania. The purpose of PASDA is to serve as the Commonwealth’s comprehensive and coordinated open geospatial data portal that provides free public access to geospatial data and information by, for, and about the Commonwealth of Pennsylvania. PASDA is Pennsylvania’s node on the National Spatial Data Infrastructure, Geospatial One-Stop, and is integrated with the National States Geographic Information Council GIS Inventory.

free data

33 Things

33 Things in your community you can map (and publish) without a GPS

Your municipality is more than just roads and parcels. There’s lots of stuff that fills in the gaps and makes it unique. With your local knowledge and recent aerial photography, you can start mapping these today.

Interested? Get in touch with us and we’ll provide you with a white paper that gives you step-by-step instructions on how to do it.

Community Features

  • Schools
  • Churches
  • Playgrounds
  • Parks
  • Parking lots
  • Municipal Buildings
  • “Centers” (Daycare, community, etc.)
  • Bridges
  • Landmarks (buildings or others)
  • Businesses (categorized as you think of them)


  • Zoning
  • Land use
  • School districts
  • Trash collection
  • Recycling routes
  • Utility service areas
  • Historic designations
  • Elm Street projects
  • Main street projects
  • Development zones (KIZ/KOZ/TIF/UGB/VGB etc.)
  • Emergency Service “first due” areas

Emergency Services

  • Incidents
  • Hazards
  • Pre-plans

Special Programs/Projects

  • Participants (member businesses)
  • Project locations (completed, under construction, pending)
  • Available locations for incubator space
  • Dollars applied for/granted/awarded/spent
  • Meeting attendees
  • Parade routes
  • Shade/street tree inventory


  • Work orders
  • Complaints
  • Permits

geo-33 things



Do I need a surveyor to map things in my community?

The long answer involves lots of caveats and what-if-but-then-again scenarios, with underlying theory and math related to spherical projection models and datums. However, it isn’t important in our context of online mapping and municipal geospatial data.

The short answer is “no” and “yes.” Here’s how to approach this issue:

Consider your purpose and stick to it

The overall  purpose of your municipal geospatial data is to provide reference-level information to your community and to provide management-level information to your municipal users. We discussed this in our last blog post. To achieve the relative on-screen accuracy that is sufficient, you can start placing pins and tracing areas from publicly available aerial photography.

When you create your sufficient data for mailbox locations (or the project of your choice) make sure to document when you did it and how you did it. You don’t need to be hung up today on whether or not you’ve created the perfect data suitable for every future use. By recording “metadata” about your current purpose, you’ll be able to provide disclaimers and reminders to other users or agencies in the future about the accuracy and precision of your data. Whatever you have done will likely be a good jumping off point for someone else in the future. Other, future, users can choose to use it as-is or refine it based on their purpose at that time.

But sometimes, the short answer is “yes.”

Within your municipal GIS, there are likely to be certain types of information that do require high precision and accuracy. An example might be modeling flows within a sanitary sewer system for capacity planning. For that type of project, you need to engage licensed professionals and the location of infrastructure should be collected by registered land surveyors.

Rules of thumb

  • If you can see it on an aerial photo and “good enough” is acceptable, start tracing!
  • Anything that needs to be located within 6 feet horizontal accuracy should be done on-site using field-grade equipment. Your own staff can do this type of work. You can find some great products for under $2,500 at Stakemill or rent equipment for short-term projects locally.
  • Anything that needs to be located closer than 3 feet horizontal accuracy should be done with survey-grade equipment by manufacturer-trained staff. You can still do this using your own staff, but the equipment costs and time commitment are higher.

Anything that requires elevation  information or horizontal accuracy closer than 1 foot should be done by a registered land surveyor.


Good Enough!

When is good enough really great? (cost vs positional accuracy of in-house data)

suf ·fi ·cient   sɒˈfiSHÉ’nt/    enough to meet the needs of a situation or a proposed end

There is always a cost to developing geospatial data. Cost can be in the form of time or in consultant fees.

Paid data geeks are always looking for data that are precise, accurate, and 100% complete, but this level of data almost never exists. And of course, the closer you get to 100% complete and accurate, the more it costs.

You can control costs and shorten development time by setting realistic requirements for geospatial data, recognizing what is good enough or sufficient to accomplish your project goals. When you set appropriate expectations, even though the quality of the information may be less than perfect the return on investment can be great.

Your data should:

Meet Operational Goals

Geospatial data for municipal government isn’t about creating the perfect product. It’s about enabling operations.

An inventory of street trees enables program oversight and strategic planning. A listing of properties that have “at risk” populations enables emergency management planning and incident response. Showing the relationship of rights-of-way and land use enables comprehensive planning and community visioning. The data isn’t the goal, getting something done is.

Sufficient data provides the level of detail you need to make the decision or find the asset that you’re concerned about right now.

Contain Cost

If you’re working with limited funding, sticking within the budget is primary. Cost overruns now will likely have a negative impact on your next project. Sufficient data is built with the recognition that time and money are finite resources.

Provide a Basis for Growth

Sufficient data allows for further expansion and refinement later. You can tighten up your accuracy by using better equipment later on, as-needed, or per-project. Make sure your data today is designed with the flexibility to add-on for future projects, but isn’t bogged down in  forecasting future use.

good enough

Triple Crown and Data Sets

Triple Crown and Data Sets

Last year, a horse named American Pharoah swept the Kentucky Derby, Preakness, and Belmont Stakes to claim the Triple Crown. This hadn’t happened since 1978 and this year, many eyes will be set to see if a horse will win the Triple Crown again this year.

Statistically speaking, it is unlikely. A quick Google search will offer up all the statistics you would ever want to study to draw your own conclusion. Only 12 horses have ever captured this prize ”“ the first being in 1919. Only 23 horses have managed to win 2 of the 3 races. Many years, the Triple Crown title is not awarded at all but 1977 and 1978 are the only time it was awarded in consecutive years.

In fact, every modern day sport seems to have its own language, statistics, and data sets.

Yet in our data-crazy world, where do many colleges and universities keep their data? If your institution is like most, you have a plan room, packed full of important campus information…and no good or orderly way to access that information. Perhaps you also have an employee who has a mind full of information that no one else knows.

Perhaps, with some work, that employee could tell you how many parking spaces you have on campus. And of those spaces, how many are ADA compliant. They may also be able to tell you the amount of linear feet of sidewalk that needs to be replaced in the upcoming season. Or show you the exact location of all campus housing in relationship to campus dining.

With GIS (geographical information system) and geospatial data, you could answer all those questions and many more, faster than I could tell you American Pharoah has 0% chance of winning the Triple Crown again – only three-year old horses can run in the Triple Crown races.

Triple Crown and Data Sets



The First Step in Municipal GIS

When it’s time to have pizza, which of these do you reach for: a phone, a frozen pizza, a bag of flour?

Your first step towards starting a municipal geographic information system (GIS) is to determine your preferred project approach. Do you want to order delivery, bake frozen, or start from scratch? Will you hire someone to do the job, have someone provide you with all the parts and pieces for your use, or develop everything on your own?

GIS Options: “The Pizza Model”
Topping Options Time to Dinner Skill / Knowledge / Effort
More Choice Quick Little
Bake Frozen

Similar to delivery,

faster than scratch

From Scratch
Unlimited Longest Significant


Municipal GIS

Municipal GIS

Why develop municipal geospatial data when we all have Google maps?

Need driving directions? Use Google Maps, absolutely.

Looking for the nearest grocery store? Use Google Maps, very likely.

Trying to find the nearest fire hydrant? Using Google Maps, probably not.

Looking for which part of town has trash collection on Tuesday? Using Google Maps, no way.

When it comes to finding things on a map we all rely on what is the closest thing at hand, our cell phone. The dominant player in mobile mapping is Google Maps. They’re on every device that you’re already using and have some of the most current road and business data available. Google Maps market dominance isn’t confined to the mobile market, it dominates desktop browser mapping as well. But when it comes to conducting the day to day tasks of municipalities you’re out of luck. Google, or any other internet mapping/search company, is focused on building data sets that generate advertising revenue. They have put maps “online” so that people can find and do business with their advertisers. Not too many people are looking to advertise the location of polling places or designated redevelopment zones and as a result you won’t find Google developing those types of layers.

If you want to use maps of your municipality to enable ongoing operations, you are going to have to build the maps (and the data shown on them) yourself. At first this will seem like a daunting task, but you can start faster than you expect. For now, don’t focus on the “how” let’s focus on just the “why”. (We’ll address “how” next with the first step in municipal GIS.)

Below are five reasons why you should collect, develop, and use your own municipal geospatial data:


By building your own geospatial data you decide what goes on the map and what doesn’t. You decide who has access to the underlying information and how it gets passed along. You won’t have to worry  about violating data licensing agreements or complying with copyright laws because as the creator you hold these rights you can do anything you want with the data. Your municipality will become the centralized authoritative single-source for local data, as it should be.


If you rely solely on data available from outside sources, you are limited to the information that they feel is worthwhile to publish. This is often a very limited set of  features (data classes or objects) because they are collecting information over a very large geographic area. As a municipality, you can decide what is important to your community. You can develop an extremely rich and broad palette of features that relates to everything that is of concern to your agencies and citizens. Google doesn’t have a layer for local parade routes, but you can have one for your town. Bing Maps isn’t publishing the location of parking meters in every town, but you can have one for your borough. Yahoo Maps won’t show you which blocks have been marked for road improvements next year, but your township can map this with very little hassle. Apple Maps won’t show you which shade trees were replaced last year but your city mapping system can do it.


When you create your own municipal mapping data you can collect as much highly detailed information as you desire. Google Maps just doesn’t provide the specificity that your municipality is looking for in geospatial data. Data collection at a national scale is very expensive, so the number of attributes (characteristics) are often limited to a small number. But with a focus on your municipality alone,   the list of attributes collected can be as numerous (deep) as needed. Municipal park locations are shown on most online maps, but they don’t regularly include helpful information for users about park hours, facility rentals or whether dogs are permitted. You municipal map can include that information as well as protected data for municipal works about the number of parking spaces, types of play equipment, acreage, and maintenance status.


Google Maps provides you with a limited set of mapping tools and you can only use them as dictated by Google’s terms of service. When you develop your own municipal geospatial data you have no limit on how to transform or repurpose the information. When you develop the data, there won’t be any hassles if you want to export municipal geospatial information to CAD for your engineering department or exchange fire hydrant locations with the 911 center.


Google Maps will always look like Google Maps. When you make a special-purpose map showing vendor locations during the local festival it shouldn’t be cluttered with extraneous labels unrelated to the event.

Google Maps is designed for on-screen use. If you want to print their maps you have very few print size options. For a poster showing voting precincts and polling places you won’t be able to do that from Google Maps. When it’s time to update your official zoning maps or assemble your next comprehensive plan you’ll be happy that the data can be formatted to multiple page sizes form within your own municipal geospatial system.

Already started your municipal geospatial project or have some questions? We’d love to hear about it, add your thoughts in the comment area below.

Municipal GIS


Your grant reporting is due, requiring details on your façade grant program. How do you keep track of all those property details and status of the work?

It’s time for the annual holiday parade. How do you inform residents along the parade route of the details for the day?

Election day is coming and your residents need to find their polling places. How can you easily create maps to post or insert with utility bills?

Speaking of utilities, are you enacting stormwater or impervious coverage fees? How will you determine who pays what?

Time for a break ”¦ for your community ”¦ so you’re closing some roads to have a special street party. How do you inform residents, businesses, and the public about the road closure?

The answer to all these questions is three little letters ”“ GIS.

Derck & Edson started exploring geographic information systems (GIS) in 1999 and we’ve been actively using it in projects since 2004. “Geospatial” is a fairly new word (first used in 1970 by the Association of American Geographers) but humans have been creating geospatial information for longer than you might think.

At Derck & Edson, geospatial information underpins how we think about campuses, downtowns, and athletics. A sense of place, literally and figuratively, is the core of what we do.

Let’s talk about geospatial data

There is no question that municipal operations are tied to place. Keeping track of assets, incidents, and operations in real-time is within the reach of local government. If your municipality is not already using geospatial data to track and manage places and things, now is the time to start.

For readers not involved in government, the same terms, concepts, and instructions presented here will apply to anyone that is looking to use geospatial information to manage assets in any type of community or site.

So in the coming months, we’re going to talk about geospatial data. Here’s what you’ll find:

Short topical overviews

Just enough text to kick-start your geospatial thinking. Our next blog topic will be along this vein and answer the question “Why develop municipal geospatial data when we all have Google maps?”

Moderate length Q&A articles

These posts will focus on questions about strategic and operational issues in geospatial projects. An example is the third blog in our series entitled “When is ‘good enough’ really ‘great’?” that will explore the trade-offs between accuracy and cost in developing in-house data.

Longer how-to articles

These step-by-step guides will dive into the details of day to day geospatial tasks. The topics will include “Finding possible rental properties” and “Developing pavement edges from PA DCNR contour data.”

Along the way

We build all of our projects from strong foundations and assume you’ll want to do the same, so we’re building a glossary of geospatial terms for your reference. The definitions won’t be what you’ll find in a text book, but something more digestible and worthwhile for relating geospatial concepts to the world around you and the things you do every day.