Understanding GIS Mapping
- May 1
- 7 min read
Updated: 11 hours ago
Since the age of antiquity man has worked diligently to navigate and traverse his home, planet earth. Whether he was motivated by conquest, necessity, or just plain old curiosity humankind has continually pushed the envelope to have a greater understanding of the third rock from the sun.
We have made incredible gains in the realm of navigation in large part due to the efforts of familiar names from the age of exploration, some of the rock stars from that time should be familiar names like Christopher Columbus, James Cook, and the highly influential Ferdinand Magellan. Magellan has a special place in history as he was the first to have a ship from an expedition circumnavigate the globe. All of this was made possible combining geometry, astronomy, and special instruments like a sextant which were the technologies of the day. These early advances in global positioning laid the groundwork for the Geographic Information Systems (GIS) positioning which has become so common place today.
Do you remember the first time you saw one of the Google cars in person as it drove the countryside and cities creating the Google maps that so many of us interact with today? That was pretty cool and for many of you reading this you may think that was the beginning of the GIS movement, but it was far from being so. Google Earth and Google Maps did create a more user friendly platform that the average person, such as myself, could understand and create with but it was not the beginning of the modern GIS revolution that we find ourselves in today.
The purpose of this article is to familiarize the reader with some of the terms that, if they haven’t become part of your vernacular already, most likely will be in the very near future. Let’s start with the term datum. A datum is a fixed starting point of a scale or operation. The North American Datum of 1983 or NAD83 is the standard horizontal reference system for mapping and surveying in North America. However, this is not the sole datum available for geospatial applications. WGS84 is the acronym for the World Geodetic System 1984. This is the standard Earth-centered 3D coordinate system used globally for mapping.
The final datum we’ll discuss here is the State Plane Coordinate System (SPCS) this is a U.S. network of specific map projections that divide each state into zones, usually following county lines, to provide m
precise, flat, grid-based coordinates
(eastings/northings) for surveying, mapping, and engineering. This system makes it easier to calculate
distances and areas rather than use latitude and longitude.
The datums listed above are some of the options available to you to collect GIS data and build maps with.
The next term we should discuss at this juncture is
RTK, which stands for Real-Time Kinematic. This positioning protocol uses GNSS (GlobalNavigation Satellite System) technology to provide centimeter level location data in real time. Prior to the advent of RTK an operator in the field might have collected data that was sub-meter…or even off by 10, 12, or 15
feet!. That’s not close enough for those of us in the utility game! In a state like Kansas,
we only get two feet either side of the line as a tolerance zone when performing a locate.
So how would I get better accuracy? The process used to be cumbersome.
You would have to take an overlay of known points and adjust the data you collected in the
field manually to improve your accuracy.
“Ain’t nobody got time for that! I have tickets that are due and water leaks to fix!” I have tickets that are due and water leaks to fix!”
Luckily, the technology that we have today is improving at an
exponential rate and the ability to collect at survey grade accuracy is
becoming common place. Survey grade accuracy is defined as highly precise with very little error at the centimeter and millimeter level.
The GIS receivers on the market today can typically collect within half a foot or less right out of the box. Most receivers can also utilize RTK networks for greater accuracy as well.
About half the states in the union even have an open and free public
RTK network option. These systems are usually erected and managed by the Department of Transportation within those states. Hopefully, Kansas will see an Open and Free RTK network in the near future like
the ones neighboring states like Missouri already enjoy. I have heard
rumblings in the field about this becoming a reality in the not-so-distant future, but no formal announcements have been made to date.
So, you may be asking yourself…What does all of this mean and how does this affect me?
Great Question!
The best reason to delve into the world of GIS mapping is simply to create better records of your infrastructure. Remember when you first started at your water district or municipality and the map you had was from 1974 and hung
on the wall? Or was it from 1874? (I have seen plenty of maps from the days of Wyatt Earp in my time) Well those days, like the Wild West, are over. The days of drawing in a map and connecting the dots (valve to valve) and calling it good as a map for your water main are fading fast. Maps can be very accurate when collected, updated regularly as changes are made to the system, and even have dynamic properties such as color changing valves to alert you when a valve needs to be exercised.
Most platforms available, such as Subsurface Maps Offline or ESRI Field Maps can be accessed via a PC or laptop but more importantly on a personal device such as your cell phone or tablet out in the field.
This maneuverability with a personal device now allows you to find a valve that has been paved over, or a meter that has been covered by landscaping with ease or even walk an entire plastic water main with no tracer wire that is unlocatable by traditional
methods using what we can consider a digital tracer wire to get that locate completed accurately and on time.
GIS receivers until just a few years ago were the only item you might find mapping capabilities in. Manufacturers’ offerings are also changing with the times. Electromagnetic locator kits like the RD8200SG by Radiodetection has RTK functionality embedded directly in the receiver to be able to map infrastructure while you locate your lines. Valve exercising equipment is available with GIS capabilities as well. Ground Penetrating Radar now has GIS abilities so operators can collect and log points for structures seen below the surface. Backhoe and grading equipment can now read a GIS map and alert an operator to the proximity to which they are digging near an underground line and alert them to a possible strike. Some backhoe models will not allow the operator to swing the boom within the two-foot tolerance zone of a line it’s reading on the map. It’s as though the boom is hitting a wall and unless you do a manual override the bucket will not be allowed to breach that tolerance zone. That level of integration means great things for all of us in terms of safety and liability when it comes to excavation and any other time we interface with our buried plant.
Get to know more about Subsurface Maps!
That’s not all…GIS data can also help us when it comes to Kansas One Call as well. Kansas One Call Contracts One Call Concepts to run the one call center and software employed by Kansas 811. That software has some functionality you’ll probably find interesting as well. You’re used to seeing a polygon showing the dig area that an excavator has called in on
a one-call ticket.
Did you know if you provide your GIS data to the one-call system they can actually overlay your data onto the ticket so you can see what you have, if anything, to go and
mark on that one call ticket? It’s true, now that’s only on your side of the portal, the excavator would not be able to see that on their end. That would be very helpful when determining how long a locate may take to perform or if you even need to send a truck to the site.
You can also utilize your GIS data as it pertains to Kansas One Call in another fashion. Their software can utilize what we call “Center Line Data”, center line data is basically a buffer zone that is specific to any GIS line or point you show on the map. Best of all you set the buffer…this can be 10 feet, 20 feet, 50 feet, etc. It’s up to you. Using center-line data instead of the traditional polygon around your entire system accomplishes a couple of different things. The
first being that you’ll get fewer one call locate requests because your notification zones are tighter and more specific to where your facilities are and not just a blanket. So, if you’re only in the front easement and someone calls in a backyard ticket beyond your buffer zone you will not be notified. The second benefit to this is that since you are notified on less tickets the amount you’re paying for one-call tickets and to be notified goes down as well. This means more time to get your tickets done when you do have them and to complete other tasks like fishing on Friday afternoons.
I had someone recently tell me the GIS boom was fifteen years ago. With all due respect I wholeheartedly disagree. Back then we were still talking about AutoCAD, stick maps, and collecting data with devices that were showing you on the other side of the road. By the way, the accuracy you’re collecting with or trying to find a known point with when using your cell phone is still around 10 to 15 feet. That’s a large search area and probably not close enough for most applications these days. Trust me, the GIS boom is now. The integration of GIS into all of the products and software discussed above on platforms the average person can utilize makes it so. With respect to GIS the prices are dropping down, and the accuracy is climbing up. I have heard a lot of folks say in my travels, “Yeah it would have been nice if we had started that 15 years ago.” My only response to them then and you now is, “Yeah and wouldn’t it be nice not to being saying that 20 years from now?” When it comes to GIS collecting it’s not so much a question of if you’re going to use it. It’s when are you going to get started.
Jeff Trowbridge
Subsurface Solutions
Area Manager
913-275-9589
Comments