The MEGUG annual meeting will be held on May 19, 1999. The location will announced in the next newsletter and on the MEGUG website.
A list server has been set up for a statewide GIS discussion group. To subscribe send the following email message to mgisuser-request@lists.state.me.us
To use the list server, just email your message to mgisuser@lists.state.me.us
The MEGUG website has been updated and is being maintained by Professor Sari Hou at Unity College. Thanks Sari!! Sari and her students will be undertaking a gradual redesign of the website over the next year. The url is:
David Carr and Chris Vera, Duke Engineering and Services
Duke Engineering and Services (DE&S) often performs many environmental analyses and mapping tasks required by the Federal Energy Regulatory Commission (FERC) for hydroelectric project relicensing. DE&S was recently involved in three hydroelectric project relicensing efforts that included several GIS tasks on the Bear River in southeastern Idaho. One of our environmental scientists was stationed in Idaho as Field Coordinator for the project, collecting data using (along with other equipment), a global positioning system (GPS), a sonar depth sounder, a laptop computer, aerial photographs, and maps generated with GIS. Work completed included the development and mapping of bathymetric contours and significant depths for the four reservoirs utilized by the hydro projects. Overall the project went smoothly, but we did learn a number of things that will help in the next project and are good "rules of thumb" for this type of study.
The technique used to develop bathymetry was to take depth readings with sonar, synchronized with the GPS for positional control. A canoe outfitted with a trolling motor was used to follow a number of transects that crossed perpendicular to the long axis of the reservoirs. Readings were taken at regular intervals (every 5 seconds), producing a sample grid of depth points. These were downloaded into the laptop and later e-mailed to our office in Portland, ME for post processing. The data was then imported into ARC/INFO for development of an elevation model and mapping.
Utilizing GPS and sonar allows data to be collected far more quickly and accurately than in the days before these tools were readily available. Learning to use the equipment is not difficult, but it's always the real world tests that provide the best lessons. We found after the fieldwork was completed that we could have designed transect locations differently. The GPS/Sonar equipment allowed depth readings a relatively short distance apart providing plenty of accurate data in a short time (one of the advantages of this technique). However, two of the reservoirs we were studying were long and thin. The transects were farther apart (200 - 500 feet) relative to the spacing of the depth points. Using the data to develop elevation models in ARC/INFO produced long, thin triangles in the TIN structure, when more equilateral triangles are preferred for the best results. Weeding out points produced a very usable TIN, but we could have developed a better model with more transects and fewer points per transect, with only a moderate increase in field time. This would be offset to some degree by a reduction in GIS analysis time.
One issue to consider in developing bathymetry in the field is the surface elevation of the water body. This is the "constant" from which the distance to the bottom is measured. In this situation, water levels are controlled by the hydroelectric dams of the project. It was important for us to work with the client to maintain as constant a level as possible during the sampling periods.
All aspects of collecting data in the field should be planned carefully. Due to project scope and budget changes, there was only one person in the canoe to steer and operate the GPS and Sonar. Although not too difficult in calm open water, there were times when our scientist had his hands full in wind gusts, choppy water or steering around rocks and shoals in shallow water. Two people would have made the job much easier and safer as well.
Base data for most of the mapping done in this project was based on USGS 1:24000 scale data. Most people using GIS today are aware of this data's characteristics and limitations, and these were made even clearer during this project. Much of the primary data was developed utilizing GPS technology and low-level aerial photography, and then mapped using a USGS base.
Project scope and budgets did not allow for field verification with GPS of shorelines, roads and other significant features.
The result was data rectification problems in almost all facets of the analyses and mapping. The most significant problems arose when we tried to match sub-meter accuracy GPS locations to the base data. Bathymetric points and contours significantly overlapped the reservoir shorelines in many instances. As many of us are aware, solving problems like these to enable accurate analysis is not easy. For these projects, after discussions with all involved parties, we used combinations of "best fit" and rubber sheeting techniques.
As data acquisition tools become more accurate and precise, our "old stand-bys" of base data are often becoming less valuable. Although not possible due to budget constraints, the use of ortho-photography would have been very valuable in this project for developing base layers. Other mapping, including cover type and land use delineation would have also been enhanced with ortho-photos.
The Bear River hydro projects provided an opportunity to use highly accurate, field derived data for GIS environmental mapping and analysis. The use of some of the latest technology proved highly efficient and powerful for gathering data. We also learned first hand some of the problems and issues that can arise in the process of taking raw field data and turning it into useful GIS layers.
The use of GIS as an information management tool in municipalities is in transition from possibility to necessity. For the past 10 years the Maine Office of GIS has provided leadership in GIS data development and sharing across agencies and with the public. Now many of the questions that have been worked out at the state level must be faced in local communities.
January's GIS Users Group meeting will provide an opportunity to discuss questions of data management, ownership, and public stewardship. Ideally, municipalities across the state will evolve data sharing relations which meet their own administrative needs, respect the privacy of their citizens, and at the same time help local businesses and nonprofit groups who can put the data to work. Nationally, there seems to be a pendulum swing at work, returning from active interest in pricing and selling municipal level data, toward a more open access policy under established local constraints.
Municipal GIS users who are interested in arguments surrounding this issue are invited to read papers concerning "fee or free?" written by UMaine's Harlan Onsrud, available online at: http://www.spatial.maine.edu/onsrud.html
Many factors will influence any local government's decisions about data management and sharing. Towns that are more advanced in GIS implementation will have perspectives to share with others who are just beginning-or just thinking of beginning. Thinking ahead to the open discussion planned for the January meeting on these themes, here are some questions that may help frame the topic:
- Who is asking for GIS data?
How can local data add to the solution of regional problems?
What can towns ask in return for data that is shared? Returns can include dollars, feedback on data quality, and empowerment of local schools and nonprofit organizations.
To what extent do state open access rules apply to GIS data sharing at the town level?
Are local policies about data sharing made by managers or through the political process?
What role is being played by private sector data developers?
Who funded local data development, and where will the dollars go that are retrieved through data sales?
Does local policy view GIS data more as a material resource that can be quantified and marketed, or as part of community knowledge infrastructure, a form of social capital?
David Kirouac, GIS Data Center, Maine Office of GIS
The Maine Office of GIS will be converting all of its GIS data from the current NAD27 (North American Datum) to NAD83 during the middle of next year (1999) - an exact date is not yet known. OGIS decided to undertake the conversion so that the available Maine GIS data will be as up-to-date as possible. Federal agencies, such as USGS (United States Geological Survey), have already begun to convert their GIS data from NAD27 to NAD83 and it is important for the State of Maine to continue to provide the best information that is possible.
WHAT IS A DATUM?
"A datum is a set of parameters defining a coordinate system, and a set of control points whose geometric relationships are known, either through measurement or calculation." (Dewhurst, 1990) The horizontal datum controls the position of mapped features in reference to latitude and longitude lines.
WHY NAD83?
The North American Datum of 1927 uses the Clarke spheroid of 1866 to represent the shape of the earth. The origin of this datum is a point on the earth referred to as Meades Ranch in Kansas. The data that was collected and the calculations that were made to estimate the NAD27 locations were done over a wide span of time (much of the data was collected in the 1800's) and were done manually. As a result, the errors in the calculations vary considerably from collection station to collection station.
With the advent of new technologies, like GPS and Doppler systems, it was discovered that the North American Datum of 1927 had some discrepancies in its accuracy. New data that was collected using the new technologies was noticeably different from the NAD27 data.
The North American Datum of 1983 was created to resolve the inaccuracies of NAD27. NAD83 is based upon both earth and satellite observations, using the GRS80 spheroid. The origin for this datum is the earth's center of mass. This affects the surface location of all latitude-longitude values enough to cause locations of previous control points in North America to shift, sometimes over 500 feet. A ten-year multinational effort tied together a network of control points for the United States, Canada, Mexico, Greenland, Central America, and the Caribbean.
TRANSFORMING BETWEEN NAD27 AND NAD83
As a result of the variations in the NAD27 collection processes and the differences in the methodologies for defining each datum, converting data from one datum to another cannot be accomplished by using one mathematical formula for each location. The currently accepted method for transforming is to use an error-averaging, rubber sheeting approach. A regular grid of control points whose datum shifts are known is used to estimate the shift at other locations.
The Maine Office of GIS will be implementing the Arc/Info command 'project', which uses the datum transformation program created by the U.S. National Geodetic Survey (NGS), known as NADCON. A minimum curvature-derived surface based upon the National Geodetic Reference System determines the transformation of points and has an approximate accuracy of 0.15 to 0.5 meters. The accepted national standard, NADCON is the fastest, simplest, and most accurate datum transformation for mapping at scales of 1:200 and smaller.
The following image is an example of the spatial difference between NAD27 and NAD83. The image compares NAD27 hydrography information and NAD83 hydrography from Augusta, Maine.
HOW WILL THE NAD CONVERSION AFFECT YOU?
Office of GIS Conversion from NAD27 to NAD83GIS data that is in NAD27 is not identical to GIS data that is in NAD83. There is a shift in the position of the GIS data that varies from location to location. This means that NAD27 GIS data cannot be overlayed with NAD83 GIS data with any accuracy (and should be avoided).
Not everybody will have to use NAD83 GIS data. NAD27 GIS data can still be used if all of the data being used is in NAD27 or if the software being used has the capability of dealing with datum conversions. All of the OGIS NAD83 data will be available from the OGIS webpage and will be available on CDs. Once the datum change becomes official: all of the data on the OGIS webpage will be in NAD83, all new GIS data that is created at OGIS will be in NAD83, and all the GIS data that OGIS will be distributing will be in NAD83. OGIS will provide more information on the datum conversion as the time nears for the conversion.
Board of Directors
- Dan Walters, Chairman, Maine Office of GIS
R. Michael White, Vice Chair, Photo Science, Inc.
Judy Colby-George, Treasurer, GeoSystems
Alexis Andrews ,Secretary, Mohr & Seredin
Nasir Shir, Education Coordinator, USM
Members at Large
- David Carr, Duke Engineering & Services
Marc Levesque, Acadia Research & Consulting
Peter Cutrone, Portland Water District
Ken Murchison, Northern Maine Dev. Community
Past President
- Tim White, James W. Sewall Co.
The promise of GIS is yet to be realized in many communities in the Northeast. In order to better communicate the uses of Geographic Information Systems and to more closely identify the GIS needs of the community, a GIS Conference entitled "Working IT" was held on Friday, September 18, 1998 at the University of Maine at Presque Isle Student Center.
This conference was held to provide a forum for the exchange of information and ideas related to Geographic Information Systems (GIS) and related technologies. Information Technologies (IT) like GIS are truly technologies on the threshold and its time to bring these technologies home to "The County". Speakers from private and public sector organizations from Maine and Canada addressed topics like Global Positioning Satellite (GPS) Data, the environment, public safety, community planning, mapping infrastructure, implementation of GIS systems, GIS and Environmental Analysis, Internet and GIS, GIS Education, Forest Management Planning with GIS and the Sable Island Natural Gas Pipeline and GIS in concurrent sessions and in round table discussions.
This initial meeting used a low-tech approach at discussing Geographic Information Systems and techniques to bring interested parties up to speed and reading from the same page on the industry as a whole. Our first ever GIS conference in Northern Maine was a great success. The conference itself was well attended and the interest it generated provided the foundation for future meetings, workshops and perhaps, a Northern Maine GIS Users Group.
We would like to take this time to extend heart felt Thank You to our sponsor organizations that made this event possible.
- Maine GIS Users Group
Northern Maine Development Commission
Maine Public Service Company
Maine Office of GIS
Seven Island Land Company
Northern Maine Technical College
Loring Development Authority
Department of Environmental Protection
Hopefully we can keep some momentum going and possibly hold another first event, the first Northern Maine Chapter of the Maine GIS Users Group some time this spring/summer. We'll be calling around to get people's ideas on this subject at a later date.
Continuing with its thirty year tradition of mapping services NMDC, with help from the Economic Development Administration, has taken the next critical step in the evolution of our Mapping Program into a true Geographic Information System (GIS). NMDC has acquired the necessary hardware and software to build our GIS Workstation. A new 450 megahertz Pentium II CPU with 128 RAM, 9 gigabyte hard drive and 1 gigabyte Jaz drive will serve as the work horse for our fledgling GIS program and is fully expandable to facilitate the future growth of our GIS program. Implementation of a true GIS system is going to help us to more efficiently relate data spatially, that is to bring data and graphic maps together using data and map sources created both in house and imported from other organizations.
ArcInfo and its companion software ArcView, a professional geographic information system (GIS) package, together with the hardware upgrades will bring the power of GIS to the desktop level. With the click of a mouse information on a geographic location can be accessed from a map on the computer monitor, this map can then be viewed together with pertinent data or themes, in the form of spread sheets and tables, to create maps for presentation or for reports. The maps can cover areas from anywhere in the world, countries, states, towns, or even a particular street in your neighborhood and by querying the data associated with these maps trends can be identified and perhaps predicted helping NMDC to make informed decisions and policies for the betterment of our programs and services.
NMDC will use the software to map census information, trends in growth patterns, comprehensive plans, economic development reports, population densities, and household income patterns in Aroostook County and beyond.
Key to our program will be the implementation of a GIS Education Program within our office in order to familiarize our staff to this new discipline and to instruct key people the utility of our new GIS capabilities. Initially our training program will be aimed at the people within our organization that have already been charge with the collection and creation of both map and data and the training itself will consist of a two day "crash" course in ArcView, combined with enrollment in the ESRI Virtual Campus. This regiment instruction will provide staff members with up to ninety days of ArcView exposure mostly at their own office workstation. In addition to ArcView training our GIS Specialist will need a battery of instruction with the ArcInfo software package which is more oriented toward programming and map overage creation.
Also of prime concern is the development of a migration path to ensure that our past mapping projects can be translated, imported or otherwise updated to ensure continuity in our evolving Mapping Department.
Our Computer Mapping Department will have its hands full in 1999. If you have any questions or suggestions concerning NMDC's GIS program please call me at 498-8736, in state 1-800-427-8736, or email at kmurchison@nmdc.org.
Chairman
Dan Walters
Maine Office of GIS, SHS#125,
Augusta, ME 04333
Ph. 207-287-3897
Fx. 207-287-7641
E-mail: Dan.Walters@maine.state.us
Vice Chairman
R. Michael White
Photo Science, Inc., 15 Cross Street Suite 75
PO BOX 979, Bangor, ME 04402-0979
Ph. 207-945-3283
E-mail: mwhite@photoscience.com
Treasure
Judy Colby-George
GeoSystems, 915 US Route 1, PO BOX 934,
Yarmouth, ME 04096
Ph. 207-846-0507
Fx. 207-846-6717
E-mail: geosys@javanet.com
Secretary
Lexis Andrews
Mohr & Seredin Landscape Architects, 18 Pleasant St.,
Portland, ME 04101
Ph. 207-871-0003
Fx. 207-871-1419
E-mail: msla@biddeford.com
Education Coordinator
Nasir Shir
University of Southern Maine, 300 Bailey Hall,
Gorham, ME 04038
Ph. 207-780-5063
Fx. 207-780-5167
E-mail: nshir@usm.maine.edu
Members at Large
Marc Levesque
Acadia Research & Consulting, 19 Karynel Drive,
S. Portland, ME 04106
Ph. 207-767-7022
Fx. 207-767-3656
E-mail: acadia@maine.rr.com
Peter Cutrone
Portland Water District, 225 Douglass Street,
PO Box 3553, Portland, ME 04104
Ph. 207-774-5961 X3107
Fx, 207-761-8307
E-mail: cutrone@pwd.org
David Carr
Duke Engineering & Services, 500 Washington Ave,
Portland, ME 04103
Ph. 207-775-4495
Fx. 207-775-1031
E-mail: dcarr@desconsulting.com
Ken Murchison
Northern Maine Dev. Community
PO Box 779, Caribou, ME 04736
Ph. 800-427-8736
Fx. 493-3108
Email: kmurchison@nmdc.org
Past President
Tim White, James W.
Sewall Company, 147 Center Street, PO box 433,
Old Town, ME 04468
Ph. 207-827-4456
E-mail: twhite@jws.com
Maine GIS Users Group
Maine Cordinates
www.unity.edu/sarihou/MEGUG.html
Publication Title: Maine Coordinates
Issue Date: December 1998
Statement of Frequency: Occasional
Authorized Organization: Maine GIS User Group
Issue Number: Vol. 4, No. 3
Notice: Mention of specific companies, products, or brand names does not imply support for or endorsement of those mentioned. Similarly, omission of specific companies, products, or brand names does not imply anything either.