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Cartography Spotlight: Coordinate System Basics

by | Jun 1, 2015 | Blog 2015, GIS

Coordinate System Basics

The challenge of representing a spherical Earth on a flat surface has posed many problems to academics of all types over the past two thousand years. The attempt to solve these problems has resulted in the systematic representation of all or part of the surface of a spherical body, otherwise known as a map projection. All geographic data has a coordinate system assigned to it so that it can be located to its actual location on Earth. There are two primary types of coordinate systems: geographic and projected coordinate systems (GCS & PCS). The details of these coordinate systems are explained later in this post. However, the figure below paints an informative picture of the primary differences between the two.

 

 

Datums

Datums are a single parameter of a geographic coordinate system that are vital in determining alignment and accuracy. The two most common datums used in North America are NAD83 (North American Datum 1983) and WGS84 (World Geodetic System 1984). NAD83 is North America-centric while WGS84 is meant to comprise a standard coordinate system for the Earth. The figure below illustrates the difference in accuracy and precision between the two. The bold line represents the actual surface of the Earth.

Datum Difference

When making decisions based on maps it is crucial to ensure that the correct datum is being used. It is important to keep in mind that despite their individual shortcomings there is no best coordinate system or datum. That varies depending on the location of the map being created and the message that the cartographer wishes to convey.

Selecting the Ideal Coordinate System

Any time that one projects a curved surface onto a flat surface there will be a distortion in shape, area, distance, or direction. The trick is to determine which projection best fits the specific needs of the map that you are creating. Below are a few quick tips for accomplishing this.

  • Databases created under contract or to be used by a government are often in a projection determined by that governing body (e.g. state plane in the United States or Great Britain Nation Grid in the United Kingdom.)
  • Use equal-area projections (e.g. Lambert, Mollweide) for thematic maps. Equal-area maps preserve area measure, but do so at the cost of distorting shapes.
  • Presentation maps are typically conformal projections (e.g. Mercator, Stereographic), although others may be used as well. Conformal projections maintain angles locally,
  • Navigational maps are typically Mercator, despite its deficiencies.

Utilize local datums if making a map of a particular area. The coordinate system of a local datum is not at the center of the earth like the coordinate system of a geocentric datum, but rather has its origin at a location on the earth’s surface. If a map area contains multiple datums, for instance a map of the border area between Eastland, Texas and Comanche, Texas, it would use the datum that covers the majority of the mapped area. Let’s say the map in questions is primarily in Eastland County, Texas. You would then use SPC S83 4202, which is the Texas North Central Zone

texas_spcs

 

Coordinate Systems in ArcMap

Defining a projection lets ArcMap know which projection your data is in for use in projecting on the fly, while projecting physically alters the source projection of the data. It is best practice to use the ‘Project’ geoprocessing tool to bring all data within the same coordinate system, if possible. Projecting on the fly uses additional resources and can harm the efficiency of your map.

What does one do if the coordinate system of the data is unknown? There are a few steps that one can take in order to be able to make an educated guess.

  • Check the ‘Extent’ box of your data in ArcCatalog.
    extent_arccatalog
  • If there are 6-8 units to the left of the decimal place, then it is most likely a projected coordinate system using linear measures of distance.
  • If the units are in decimal degrees, one can be certain that the data is in a GCS.
  • Once you have an idea of the projection type and units, the rest is trial and error. If you know that the data is based in North America then you will most likely use a UTM or state plane coordinate system.
  • You may test your hypothesis by defining the projection in the feature class properties and seeing what happens. As stated before, this process may take some trial and error to achieve the desired results.

Conclusion

The first map projections held sparse information, but the cartographic community has since made tremendous strides. Still, it is key for any GIS Analyst to understand the pitfalls and advantages of various coordinate systems. Map projections not only affect the aesthetic of a map, but can also present an inaccurate depiction of its underlying data. At InterDev, we possess a keen understanding of these cartographic concepts and employ them in all of the maps that we create. For us, there is no way to create a great map without it first being an accurate map. This level of attention to detail permeates everything that we do.

 

Chris Rice

GIS Analyst I

crice@Interdev.com

As CEO of InterDev, Gary Nichols leads a firm of over 75 professionals, working from Atlanta and Chicago offices, who serve a variety of clients throughout the Southeast and Midwest. Nichols is responsible for managing the company’s direction and overall operations. He also spearheads InterDev’s initiatives in outsourced Managed IT and communications, overseeing its professional services and support to government, education, business and non-profit organizations across the US.

As the founder of InterDev in 1980, Gary was an early adopter of innovative technologies ranging from the first personal computer to artificial intelligence. His personal mantra of “find a way” inspired the innovative Government IT Consortium, a shared-service outsourcing model in use in the Chicago area. Gary’s leadership led to the formation of successful public-private partnerships (PPP) with the City of Sandy Springs, the City of Brookhaven, the City of Dunwoody, and other municipalities in Georgia.

Since 1980, the InterDev team has accumulated multiple industry awards, including Atlanta Business Chronicle Pacesetter, Appen Media Best of North Atlanta, and Inc. 5000 Fastest Growing Private Companies in America (three-time honoree) – all under Gary’s leadership.

Gary earned a Bachelor of Business Administration from Georgia State University and is a Certified Information Systems Security Professional (CISSP). He is currently working on a Master’s Degree in Cybersecurity at the Georgia Institute of Technology. Gary has served on the Advisory Board of the National Technology Security Coalition and volunteers with TAG-Ed, FutureCity.org, and Habitat for Humanity.

With his extensive expertise in information technology and systems security, and strong professional training in IT solutions ranging from data centers and cloud computing to networking, Daniel Schultheiss is the cornerstone of InterDev’s IT practice. He provides high-level analysis of the IT infrastructure of organizations – from corporations to municipalities – and offers recommendations on how they can achieve their goals.

During his tenure at InterDev, Daniel has played a key role in InterDev’s growth, as the firm expanded its expertise to embrace emerging technology and security disciplines that have now become mission critical to firms of all sizes. One of his most significant achievements was helping to develop and implement InterDev’s Managed Services platform in 2006 – his first year with the firm. He also served as IT Manager for the City of Sandy Springs from 2011-2013, and helped InterDev launch its Government Services division in 2014.

Daniel holds a CISSP certification and is a Certified Ethical Hacker. He is also a member of the Technology Association of Georgia (TAG). Daniel graduated from the University of South Carolina in 2006 with a Bachelor of Science degree in Computer Engineering.

Neil Matchan leads InterDev’s technology programs, using his expertise and vision to help InterDev identify and seize technology opportunities for its clients while they are still in the innovation phase. Matchan was instrumental in developing, managing and growing InterDev’s Managed Services program, one of its core offerings.

Neil joined InterDev in 1998 as a Senior Systems Engineer, putting his strong technology acumen to work on the firm’s behalf. In 2006, he was promoted to the position of Director of IT Services, overseeing InterDev’s Technology Department and all related projects and client interactions. In 2014 he was promoted to CTO, a role that more clearly represents the contributions he makes to InterDev to this day.

Prior to joining InterDev, Neil worked in corporate sales for CompUSA, where he was named a Top 30 performer in the nation and was the #1 Account Executive at his location from 1995-1998.

Neil holds certifications from Dell, Barracuda Networks (Spam, Message Archiver, Load Balancer, and Web Filter), VMware, and Ruckus Wireless as well as for most major corporate software and hardware manufacturers. In 2009, he became the first person to be certified as a Next Generation Engineer through Barracuda’s firewall specialist program. Neil studied Industrial Psychology at Georgia State University and is a graduate of the Network Administrator Specialist program at Oglethorpe University.

As Chief Government Information Officer, Ashley Smith provides vision and leadership for developing and implementing information technology initiatives for InterDev’s Government Services division. He also acts as the Virtual Chief Information Officer (vCIO) for more than 20 of InterDev’s client municipalities, providing short- and long-term strategic IT planning for their environments.

With an extensive background working in the information technology and services industry, Ashley’s insight and planning have helped position InterDev’s municipal clients as leaders in the government sector, and he and his team continue to help these clients set the bar for exceptional municipal services.

Even before joining InterDev, Ashley was a seasoned government IT professional at both the state and local levels. He previously served as the IT and Communications Manager for the City of Hapeville, Georgia and as the IT Manager for the Hapeville Wi-Fi Network, part of the Wireless Community Georgia Grant program sponsored by the Georgia Technology Authority.

A frequent presenter at the Georgia Municipal Association’s Annual Conference and the Annual Mayors’ Day conference, Ashley has taught classes on best practices in government IT and on using technology to improve government operations. He holds a Master of Public Administration from Georgia Southern University and is a certified Government CIO (CGCIO) and a Cisco Certified Network Associate (CCNA). He is also certified in Network + and GCIC Data Integrity, and has completed courses in Recovery Training and Project Management from the Department of Homeland Security.

As InterDev’s Director of Operations, Mike Edelson oversees a consortium of local government GIS Managers throughout the Atlanta metropolitan area and manages InterDev’s MosaicGIS cloud-based solution and Location Intelligence Labs. With more than a decade of experience in Geospatial and GIS technologies, Mike has strong expertise in GIS enterprise database design and management, GPS collection and processing, and SDSFIE & FGDC metadata standards.

Mike joined InterDev in 2013 as a GIS Analyst for the City of Brookhaven, Georgia as part of InterDev’s public-private partnership with the city. After building the Brookhaven GIS department, he became instrumental in shaping InterDev’s GIS program and services for dozens of cities. His recent promotion to Director of Operations solidifies his commitment to leading the company to the next level of sales and service.

Prior to joining InterDev, Mike worked as a Project Manager at CH2M Hill, a global engineering firm. Working for the military, Edelson provided GIS Military Master Planning services to more than a dozen US military installations throughout Afghanistan, Iraq, Kuwait and Qatar. He also performed field work after Hurricane Katrina.

During his career, Mike has received numerous awards, including URISA, a nonprofit professional organization that awarded Mike and his team the prestigious Exemplary Systems in Government Award in 2014 and 2016. Since 2012, he has volunteered as a Judge for the National Engineering Week Future City Competition. Mike holds a bachelor’s degree in Geography and Environmental Science from Florida State University and is a graduate of the Leadership DeKalb Academy.

Lewis Wilkinson, Sr. heads InterDev’s Project Management Office, where he and his team work closely with government, commercial, and vendor principals to ensure the success of project work and the satisfaction of all parties. With a deep understanding of the complex interactions of software and technology deployments – and how they impact business processes – Lewis provides the structure, guidance, and communications to promote optimal results for InterDev clients. Projects Lewis successfully manages involve enterprise-wide ERP software, security and risk management assessments, technology infrastructure upgrades, and Managed Services deployments.

Since joining InterDev in 2011, Lewis has helped to build InterDev’s Project Management Office. He has also worked extensively with BS&A, Tyler Munis, Tyler Incode, New World Systems, CIS CSC security framework, and the ESRI GIS software suite, helping InterDev and its clients reap these platforms’ benefits.

Lewis is a certified Project Manager (PMP) as recognized by the Project Management Institute and an Agile Certified Scrum Manager (CSM). He holds a Bachelor of Arts in Sociology and Computer Science from Wake Forest University.

With a mission to provide, establish, and deploy the best security practices for InterDev and its clients, Jesse Cail leads InterDev’s Security team with the dedication to excellence he has shown in every facet of his life. As an information security professional with a broad spectrum of expertise ranging from cybersecurity and communications to windows and server administration, Jesse is laser focused on systems security and information assurance for InterDev clients.

Jesse joined the InterDev team in 2012 and almost immediately leveraged his experience and strong domain administration skills to build a security program from the ground up for the City of Sandy Springs. This program would later serve as the model program for all of InterDev’s clients.

A retired U.S. Army veteran with unique experiences in Special Operations, Jesse served and deployed with both 3rd Special Forces Group (Airborne) and 5th Special Forces Group (Airborne). He was also selected for a special six-year assignment to the White House Communications Agency, served as a member of the White House Situation Support Staff, and directly supported the White House Situation Room and National Security Council.

Jesse holds a Bachelor of Science in Information Systems Management from the University of Maryland. He is a Certified Information Systems Security Professional (CISSP), a GIAC Certified Critical Controls Implementation/Auditor, and a certified GIAC Security Essentials practitioner (GSEC).

Jennifer Braithwaite, InterDev’s Business Development Manager, leads her team by developing key relationships throughout the Southeast region in collaboration with the Government team at InterDev. Her talent and ability for building business relationships enables her to connect naturally with InterDev clients and prospects, making her a highly valued team member. Always focused on company achievement, Jennifer challenges the team to identify potential opportunities and helps them develop and execute the strategies that will bring them – and InterDev – success.

After joining InterDev in 2012 as a Sales and Marketing Assistant, Jennifer has logged an impressive track record. In 2014, Jennifer began selling for InterDev full time, landing several major accounts. In 2015, she was promoted to Business Development Associate after more than doubling her sales by securing over $2 million in revenue. Jennifer was also instrumental in helping InterDev land engagements with the City of Beaufort, South Carolina, and the cities of Canton, Chamblee, Douglasville, Fairburn, South Fulton, and Stonecrest, Georgia. In 2017, she was named to the InterDev $5 Million Dollar Club for another year of record-setting sales.

Prior to joining InterDev, Jennifer held a series of progressively responsible administrative positions, gaining operational insight that informed her work helping municipalities recognize the value in robust IT structures. She is a member of the Georgia City-County Management Association, the South Carolina City-County Management Association, the Texas City Management Association, the Florida City-County Management Association, Government Management Information Sciences, and the Georgia Municipal Association. She has also been named to the InterDev $5 Million Dollar Club for record-setting sales.

As IT Manager of InterDev’s Midwest region, Nino Spuria is a high-performance IT leader focused on building, growing, and managing InterDev’s advanced IT service structure. His strong technology background, combined with strategic leadership and business acumen, gives him the ability to meet or exceed service excellence goals while also increasing revenue and client satisfaction.

Prior to joining InterDev, Nino built a remarkable legacy of technology-focused project management and execution, especially in the public sector. As VP of Service Delivery at SDI, he was instrumental in the City of Chicago Mayor’s public initiative to install 1500+ cameras in more than 70 rail stations within six months to increase public safety and security.

A recipient of more than 15 awards for performance/delivery excellence from IBM, marchFIRST Inc, and SDI Solutions, Nino is ITIL certified and holds a Bachelor of Science in Statistics from McMaster University.

As IT Services Manager, Rosie Caldon leads a highly skilled and specialized team of engineers and customer care staff dedicated to providing professional technical support for all IT and VoIP products and service offering. Their dedication to maintaining the human element in technical support through personable, live-answer service promotes InterDev’s positive customer experience.

Rosie Caldon joined InterDev’s Voices Services Team in 2016 where she quickly expanded the company’s client base to more than 300 Commercial and Government VoIP clients and has subsequently been a key contributor to the success of onboarding enterprise VoIP clients.

Caldon’s career expands more than 10 years in the Telecom and IT industries in roles ranging from customer support to installations, project management, training, and leadership roles in complex and diverse technical environments.

Rosie studied Sociology at the University of Georgia and maintains her industry expertise through attainment of partner certifications with such innovative leading providers as Avaya, Jive, Digium, Fuze and Fortinet.

Jeff Colonna joined InterDev in 2019 in the role of Corporate Controller. In this position, he is responsible for the leadership of all accounting and finance functions. Since joining the firm, he has successfully transformed many of the financial processes of the company by incorporating new technologies that promote efficiency.

Colonna began his career with the international accounting firm Deloitte, where he specialized in auditing publicly traded technology companies. He later moved to the corporate accounting sector where he held several controller and director-level roles with small and large technology companies.

Colonna earned a Bachelor of Science in Accounting from the University of Connecticut and is currently a licensed CPA in the state of Georgia.

Randi Russell is the Human Resources and Recruiting Manager for InterDev, a role she assumed when she joined the company in 2018. In this position, she is responsible for all human resource functions from onboarding to professional development and exit planning as well new hire recruiting.

Prior to joining InterDev, Russell worked for a large retailer where she gained experience in warehouse, distribution, inventory control, risk management and human resources. Among her other professional accomplishments she counts the successful establishment and operation of a food distribution company that she grew to $8MM in annual revenue over nine years as well as an extended tenure working in the commercial furniture industry where she attained increasing levels of responsibility in business operations, commercial services and human resources.

Russell studied Liberal Arts and Computer Science at DeKalb Community College in Clarkston, Georgia, and earned her certification as a SHRM-CP in 2018.

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