Welcome! 


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BlackWatch
Posts: 14
Location: Orlando, FL USA

Joined: 10/17/2008
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Welcome to GIS: Outside the Boundaries, the discussion forum for GIS professionals and practitioners.  The name is intended to reflect three realities.  First, that we can talk about anything related to GIS and its practice here.  We can live outside the boundaries.  Second, that the essence of GIS is that it operates beyond the boundaries of any single parcel.  If you try to put all those parcels surveyors describe into a GIS database, some aren't going to play well with others.  It's your job to make them all fit.  To do so, you have to move outside the boundaries.  Lastly, what GIS folks do is usually outside the boundaries of making maps.  We have to design and construct software and computer databases.  We have to figure out how to do things that have not been done before.  We have to adjust our methods to fit our data, which does not conform to some legislated quality requirements.  We know that the best data is the data we have.

This forum will only be as good as you make it.  Ask questions or answer them.  Post opinions or respond to them.  Be bold.  Be inquisitive.  Be honest.  Behave.  But, most of all, participate.
  Friday, October 17, 2008 at 10:54:47 PM
Thomas LaCorte
Posts: 62

Joined: 10/17/2008
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How does a surveyor that has been doing boundary and topo work all his life find his way into the GIS market? And by that I'm asking how can I take my expertise and knowledge and my RTK equipment (that is sitting idol because of the current economy) and fill a need in the GIS
industry? Where does one go to find GIS field work and only field work? Because the rest of the GIS process I would just as soon leave it to the ones who are already involved with it. I need field work and I can provide the data you need in the office. How can these needs be brought together? 
  Wednesday, November 12, 2008 at 10:23:55 PM
BlackWatch
Posts: 14
Location: Orlando, FL USA

Joined: 10/17/2008
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The brutal truth is that the GIS market generally doesn't need the kind of accuracy and resulting cost generated by traditional surveying process.  Even a scale of 1" = 100' is consider very large by GIS standards, and it only requires accuracy of plus or minus a meter.  The "G" in GIS is geography, which means the field is concerned with large spaces.  Line widths are several feet wide and point symbols are yards across at scale.  GIS deals with spatial relationships in a large extent.  It's not that GIS cannot work with high accuracies, it's that the applications don't need it.  GIS is authoritative with regard to relative location at geographic scales, not absolute position in the real-world.  I don't know of any agency that compiles general GIS data using survey processes.  If you want GIS field work, then you will generally have to use GIS methods to compile it and leave that RTK equipment in the closet.

The only typical exception for GIS data collection using surveying methods is utility facility data.  Here, we are generally referring to engineering-grade GIS data with accuracies approaching plus or minus one foot with multiple facilities in a reasonably small area where RTK set-up may be justifiable.  This is particularly the case where the usual differential GPS unit will have trouble due to tree cover and urban canyon effects.  But there are very few of these projects.

If you want to stay in the office, you could get into the cadastral mapping business.  In this work, you will utilize some of your "art of surveying" skills to resolve inconsistencies between adjacent surveys.  But you won't be doing so as a surveyor.  You will need to make a call based on the evidence available in the office.  The cadastral mapping rules of the state department of revenue controls here, not the surveying statute.  Typical prices are in the $8 range per parcel for this work.  You won't be able to afford to go do a lot of research.  And if you are working in a non-PLSS state, then there may not be anything to research.  I have worked with two mapping efforts where at least 30% of the county had never been surveyed, and in one they accepted property descriptions on the order of "five (5) acres, more or less."  No sketch or plat to reveal the new parcel's shape.  No indication as to where the five acres may be located.  Just a reference to the parent parcel.

The realities of GIS is why I say that licensure under surveying statutes has no use in the GIS world; none of the surveyor's practice standards really apply.  You will need to be much more concerned with collecting descriptive attributes and creating a useful database design when doing GIS work than you will be with compiling the location data.  So, the bottom line is that if you are looking for work in the GIS field, it normally will not require many of your typical surveying field methods.  But, if you are willing to use different methods and equipment, then you can get work compiling data for GIS applications.
  Thursday, November 13, 2008 at 7:24:26 AM
Thomas LaCorte
Posts: 62

Joined: 10/17/2008
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Thank you so much for a most informative answer! I learned so much in the fast scan I did of your reply(just got home from the field) I will really digest it later.Again thank you very much!!
Sincerely, Tom(in Orlando)
  Thursday, November 13, 2008 at 5:59:45 PM
Isleno
Posts: 42
Location: Gonzales, La USA

Joined: 10/20/2008
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  I don't know how anyone can "resolve inconsistencies between adjacent surveys" while sitting in the office.  It is bad enough that imprecise deed descriptions are plotted and mapped as if they were perfect, now we are talking about manipulating data to resolve inconsistancies.  GIS must never be used to resolve inconsistancies.  If there are adjacent surveys that are in conflict, map them that way!  Some day it will be important to resolve the inconsistancies and a compentent surveyor will do it in the field by recovering boundary evidence.  Geeze Louise!
  Sunday, November 30, 2008 at 7:17:42 PM
BlackWatch
Posts: 14
Location: Orlando, FL USA

Joined: 10/17/2008
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You cannot map adjacent parcels as discontinuous if your task is to produce a property map of the jurisdiction.  Such maps can have one and only one property owner for each parcel, and every inch of the jurisdiction's extent has to be in a parcel.  Property mapping for assessment is done to the requirements of the state department of revenue, not those of the surveying profession.  The goal is assessment, not precise delineation of boundary.  Twenty acres that are not precisely displayed on the map are still 20 acres with the proper assessment value based on general location.
  Sunday, November 30, 2008 at 7:24:10 PM
Tom
Posts: 5

Joined: 11/17/2008
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In some of the technical sessions I've attended at surveying conferences, I've heard surveying/engineering firms tell how when they did GIS work for a municipality, they used the same accurate GPS methods they would for other types of surveying. This is because it costs about the same when you go out in the field and set up your equipment; you might as well get it as as accurate as you can to get more bang for the buck. Even if a customer doesn't need centimeter-accurate data now for its GIS, an application may come up down the road where they do. They won't have to go back out in the field, as they'll have the data on hand.

One simple case I've always cited that illustrates the need for accuracy in GIS is if you're mapping manhole or utility pole locations for a municipality's GIS. If you find two of them in a street 6 feet apart, you obviously need to be accurate enough to differentiate that.

Tom Gibson, PSM editor
  Wednesday, December 31, 2008 at 12:33:22 PM
BlackWatch
Posts: 14
Location: Orlando, FL USA

Joined: 10/17/2008
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I understand your point, Tom.  However, most GIS databases are as equally concerned about time as they are space.  This means that the precision and resolution of a location represent a position at a point in time.  Greater spatial accuracy requires greater temporal accuracy, which is why most boundary surveys "expire" after 90 days or so.  The same applies to GIS data.  The more accuracy you provide, the more frequently you have to recompile the data.  GIS data is all about phenomena membership, attribution, and relative location, because GIS deals with spatial and temporal relationships; i.e., the relationship of one phenomenon to another at a point in time.  A map is one way to express such a relationship, but mapping is not the objective of GIS.

The result of all this esoteric stuff is that the two manholes that are six feet apart can be distinguished in the GIS database using a location attribute but will appear to be coincident on a map up to a scale of 1 in. = 50 ft. or so, which is a huge scale for GIS.  This is because the point symbols you will use to show the location of the manholes will really be a circle of at least 1/16 in., which is a scale size of about 3 ft. in diameter at 1" = 50'.  Because GIS deals with relative position, everything on the map will also have to be displayed at this scale, which requires a resolution of +/-1.5 ft. on the ground to meet national map accuracy standards.  This means that everything--road edge lines, sewer lines, water mains, etc.--will also have to be compiled at that level of accuracy, which is nearly impossible for water lines, at least.  (You can usually assume sewer lines are straight between manholes.)  Even Zip codes and census tract boundaries will need to be properly aligned.

That is what you have to do at the large-scale end of the spectrum.  What about the small-scale end?  There, you run into the issue of having to cartoon the map image to be sure that those manholes show up as separate points at the more typical scales of GIS, like 1" = 200' or less.  This is especially true with water valves and fire hydrant assemblies, where the various instances may be located wthin a foot or two of each other.  The result is that the only place to put the real location description (rather than the one inferred by the map position) is in the database.  Many GIS databases use a display scale setting to switch between different scale-dependent map layers to properly show facilities as distinct with a minimum of distortion.

The key to a useful GIS database is consistency.  Since the objective is to map relationships, all thematic layers of the database must be compiled to the same standard.  You can't just compile manholes with a high degree of accuracy, overlay that data on a typical GIS base map, and call it a day.  If you are going to use high-accuracy thematic data in a GIS, then all the data in the system must be high accuracy, not just what the surveyor gives you.

The solution to the apparent conflict is for the surveyor not to use the traditional methods of compiling data.  Surveyors need to be more flexible and learn how to utilize lower precision methods when supplying data to GIS clients.  Not every job needs the same level of precision.  Surveyors must go well beyond measuring position to serve the GIS client.  Less can be more.
  Wednesday, December 31, 2008 at 1:21:51 PM
sideshot
Posts: 6

Joined: 10/20/2009
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Can you give an example of a typical field data collection set-up for GIS? Also, what exactly is the deliverable?
  Tuesday, October 20, 2009 at 11:13:26 PM
BlackWatch
Posts: 14
Location: Orlando, FL USA

Joined: 10/17/2008
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A submeter (meaning real-time differential correction) handheld GPS unit, such as sold by Topcon, Magellan, Trimble, and others running ArcPad or equivalent software is a typical configuration that costs around $4,000 is what you need for field data collection.  In the office, you would use something like ArcView (the lighter version of ArcGIS) to work with the shapefiles created in the field.  The deliverable is usually a set of points compiled using the field unit, such as for as-built information following utility installation (representing manholes, meters, valves, etc.) along with data about each point (type, class, date installed, etc.).  Frankly, the attributes are generally more important than the precise location, as what you are collecting are usually highly visible objects.  I have compiled survey corners this way to register plats for COGO processing in non-PLSS states where 1:1200-scale display is the largest to be used.
  Wednesday, October 21, 2009 at 6:46:01 AM
monosco
Posts: 1

Joined: 7/30/2012
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This image should serve to remind us that the enemy we perceive in GIS might actually be the window of opportunity. Let's not squander it! http://tinyurl.com/d5cpnv4
  Monday, July 30, 2012 at 3:32:07 PM


 
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