Visualizing an Intervention for Tobacco Control

Submitted by Jennifer Rewolinski

Dr. Heckman, an assistant professor of psychiatry and behavioral sciences at the Medical University of South Carolina (MUSC) in Charleston, used Community Health Maps (CHM) tools in his research on tobacco control. Smoking is the leading preventable cause of death worldwide and costs the US $130 billion in direct medical costs annually. Smoking is still a major public health issue that influences mortality, morbidity, healthcare costs, the environment, and quality of life.

Dr. Bryan Heckman

The outcome of Dr. Heckman’s precision medicine project will be a mobile app that aids smokers who recently quit by alerting them of proximity to stores which sell cigarettes or alternative nicotine products. Studies show that greater tobacco retailer density is associated with greater incidence of relapse; Dr. Heckman believes that mapping provides a new approach to visualizing environmental factors. A CHM training event at MUSC spurred his decision to integrate mapping into his own work using the CHM labs as a guide. These labs provide step-by-step instructions for implementing the CHM workflow. He used the data collection app Fulcrum on an iPhone to collect information on retailers: GPS coordinates, type, type of tobacco products sold, e-cigarette advertising, and photos. His team also used a high-powered Trimble GPS device to test accuracy of phone GPS, and the accuracy of phone GPS was adequate and more cost effective than more expensive GPS devices.

Figure 1. Dr. Heckman’s in progress map shows higher numbers of tobacco retailers are associated with  Census Tracts that have both higher poverty and a higher percentage of minority populations.

Dr. Heckman integrated his Fulcrum data into QGIS software. He added national datasets from the American Community Survey and Behavior Risk Factor Surveillance System for Census tract data, and Synar for retailer data to check the validity of the Fulcrum data; field data collection with Fulcrum revealed a more accurate list of current retailers than the national secondary datasets provided. Dr. Heckman believes QGIS is a powerful tool with many features; he was not only able to use QGIS to monitor and visualize his research questions but also to guide his project decisions and hypotheses. His results will guide policy recommendations, improve access to care, and deliver novel interventions.

Figure 2. Dr. Heckman’s in progress map shows higher numbers of tobacco retailers are associated with Census Tracts with higher percentages of minority populations

For those attempting to undertake a health GIS project on their own, Dr. Heckman emphasized that all the tools needed are provided on the CHM blog; only time and patience are required. He also recommends asking for help and reaching out to other CHM users who have experience. Dr. Heckman’s project has the potential to affect behavior change and reduce health disparities via a mobile intervention app which identifies nearby tobacco retailers and prompts and provides an intervention and awareness of a health issue. Dr. Heckman’s experience is an example of how the CHM blog and tools might be used.

Dr. Heckman would like to thank Kurt Menke and the CHM team, Dr. Williamson from MUSC, and his mentors for inspiration and growth. He would also like to acknowledge the Hollings Cancer Center and American Cancer Society Institutional Research Grant that helps support his work, and Alex Hirsch for his help coordinating the project.

The CHM team would like to extend their own gratitude to Dr. Heckman as they sincerely appreciate his time and his support of the CHM blog.

Mapping Curb Ramp Accessibility around a Silver Spring, MD Assisted Living Facility

Submitted by Jenny Rewolinski, University of Maryland, B.S. Community Health 2016I just completed a spring internship with the National Library of Medicine (NLM). My goal was to demonstrate what a typical user of the Community Health Maps (CHM) blog might experience, while using the low cost resources it reviews to develop a mapping project with a public health focus. I read through the case studies on the CHM blog and used its labs to develop my project plan and to guide my related decisions.Because of my experience with elderly relatives and my background in public health, I centered my project on how the senior population of a nearby Assisted Living Facility might safely navigate local sidewalks. According to the 2014 American Community Survey, 23% of people over 65 have some sort ambulatory disability. With this in mind, I decided to map local curb ramps --sloped transitions between sidewalks and streets which function as accessibility enhancements to help those with mobility issues to cross streets safely.I used CHM Lab 1: Field Data Collection to learn how to design my own data collection form using iForm. My Curb Ramp form captured curb ramp location, conditions, and other observations such as seniors using the curb ramps, steep or damaged curb ramps, and a lack of sidewalks in the area. As discussed in a prior blog post, How Accurate is the GPS on my Smart Phone?, phone geolocation is usually accurate up to 8 meters. This was not precise enough for my curb ramp data, so I corrected for this on my form.  Over the course of 8 hours spanning 2 days, and with 2 other interns I collected 103 existing curb ramps and locations where curb ramps might aid accessibility.Next, I brought my iForm curb ramp data from my phone into the QGIS software by using instructions from CHM Lab 2: Bringing Field Data into QGIS.  I also used CHM Labs 3: Combining Field Data with Other Organizational Data and CHM Lab 4: Basic Spatial Analysis  to add data layers and to perform spatial analysis to finalize my map.This is my project map! I completed construction of my map using CHM Lab 5: Cartography with QGIS. In addition to my curb ramp data points, I added data layers for sidewalks, roads, places of interest (such as grocery stores, restaurants, bus stops,  theaters), and my Assisted Living Facility. My goal was to raise awareness of how accessibility can impact seniors’ sense of autonomy and empowerment, and their ability to exercise and to lead a healthier lifestyle. This map also provides recommendations for where more curb ramps should be placed based on observations during data collection. I plan to discuss this map and curb ramp recommendations with the city of Silver Spring and to create “safest route” guides for popular local destinations.GIS has a huge potential to help us analyze health issues. When I began my project at NLM, I thought I would simply be mapping the location of curb ramps near a local Assisted Living Facility; however I discovered the significant need for more curb ramps as well as sidewalks around my project area.I believe the conclusions I was able to reach by using the low cost CHM resources CHM are accurate and workable. I came to NLM with little to no GIS knowledge yet I learned from the CHM GIS labs, collected curb ramp data points and created a map that may bring awareness to a public health issue. In doing so I believe my experience is typical of many CHM users.

If I can do it, you can too!

Fulcrum Updates The App Designer

We introduced Fulcrum in a recent post and are very impressed with this tool. Recently Fulcrum updated their App Designer. Fields are now divided into categories from the most common and basic fields, to the most advanced.  The groups of fields have also been color coded from green to red to make this arrangement more intuitive. The five categories are: Basic, Choice, Design, Media and Advanced. At the top are Basic fields which include Text, Numbers, Date etc. This reorganization makes finding fields and developing a form even faster.One category of interest is Design. These are fields that can be used to organize your data collection form. Sections allow you to divide your form into parts. For example, you could separate your main survey questions from your data collector metadata questions. The example App below has two sections: Main section and Data Collection Information.Organizing your questions like this can help data collectors complete the form, especially for form with a lot of questions. The screenshot below shows how the above form is rendered on a smartphone.In future posts we will give some helpful hints to working with Fulcrum including sharing forms, managing data and downloading data. Stay tuned!

Community Health Mapping: A New Year Review

To start the New Year I thought I’d begin with a review of Community Health Mapping (CHM). There are a lot of new project partners, and I thought it would be a good time to give a project overview. CHM is a collaborative effort between the National Library of Medicine, Center for Public Service Communications and Bird’s Eye View. The National Library of Medicine is funding the initiative.The overall goal is to empower community organizations serving vulnerable or underserved populations with low cost, intuitive mapping technology. Therefore we’ve been working with programs organizations who:

• Focus on vulnerable populations
• Frequently use and collect data
• Need effective, scalable & easy to use mapping tools
• Lack resources (i.e., for proprietary GIS training & software)

We have identified a suite of tools that allow you to collect custom field data, analyze that data, combine it with other spatial datasets, and generate both static maps and/or dynamic maps on the internet. This allows organizations to collect and work with their own data, and if appropriate, share it with others. CHM involves three components that meet all basic mapping needs:

• Field Data Collection
• Desktop Analysis and Cartography
• Internet Mapping

A given project may not require all three, however, collectively these components address the basic needs of all mapping projects.Field Data Collection:Rather than focusing on the use of expensive GPS receivers, we recommend the use of smart phones and tablets for these reasons:

• Most community-based organizations already have them!
• Many know how to use them
• They're intuitive
• They're portable
• They come with an on board GPS receiver (iPhone 5 uses GPS + GLONASS)
• Have on board cameras
• Can connect to wireless networks
• Access to the internet
• Email is available
• “There's an app for that!”

Of course an important consideration is horizontal accuracy. You can read our blog post on that topic to see if mobile smart devices meet your project needs.When collecting data you need to be able to develop your own custom data collection form. The top three mobile apps we have found are:

• Fulcrum: Easiest to use - iOS & Android – low monthly subscription - http://www.fulcrumapp.com/ 
• iForm: Slightly steeper learning curve – iOS and Android – free account - https://www.iformbuilder.com/
• ODK Collect: Easy to use – Android only – free account - https://opendatakit.org/use/collect/

Desktop Analysis and Cartography:After community field data collection, the next step typically involves bringing the data into a desktop GIS. This is the middle step in the workflow. Here the data can be viewed against basemaps such as Google or OpenStreetMap, and combined with other organizational data. This is also where analyses (proximity, density etc.) can be conducted. Presentation quality maps can also be generated in this step.The software we found to be the best fit is QGIS. This is an open source desktop GIS software. It has many strengths:

• It can consume many kinds of data, including all the data that would come out of the field data collection apps.
• It is both intuitive and robust.
• It has a large suite of geoprocessing tools for analyzing data.
• It will run on Windows, Mac, or Linux.
• It is free to download and install.
• It is well documented.
• There is a large user community.
• New functionality is being continuously added. New stable versions are being released every 4 months!

Web PresentationOften you may want to present an interactive map of your results. Interactive means the map reader can zoom in/out, pan the map and turn layers off and on. For this we recommend CartoDB.You can sign up for a free account, which gives you 50Mb of storage space. Data can be collected with a smart phone or tablet and brought directly into CartoDB.  It is a very intuitive platform. You can literally drag and drop a spreadsheet onto the CartoDB page and have the data upload to your account.  It will accept the most common geospatial file formats including: spreadsheets and comma delimited text files with addresses or coordinates, KML/KMZ, GPX, and shapefiles.CartoDB also has great documentation including:

• CartoDB Editor Documentation
• A comprehensive series of tutorials breaking tasks up into Basic, Medium and Advanced categories
• Tips and Tricks
• FAQ’s

In ConclusionThis blog has a lot of resources including reviews of mapping technology and case studies. You might begin by clicking on some of the links in this entry. We are also working on a 6 lab CHM curriculum that interested parties will be able to use to hone their skills. Stay tuned for that!We are always looking for new partners and continuously work to support current project partners. If you are interested, or have questions please don't hesitate to contact John Scott (jscott at cpsc.com) or Kurt Menke (kurt at birdseyeviewgis.com). Most importantly get out and do some mapping in 2016!   

Field Data Collection with Fulcrum

Fulcrum was reviewed in our initial survey of field data collection apps in 2012, and almost made the top three. In the last 3 years Fulcrum has improved and has become perhaps the most intuitive and useful data collection app we've evaluated period.It is available for both iOS and Android. It isn't free, but the subscription fee is affordable. It costs anywhere from $18 - $25 per month. The three pricing plans give you 10 - 30Gb of online storage, which is substantial. Fulcrum offers a free 30 day trial which includes all the functionality. You can use this option to test Fulcrum for your projects. In the following example, I will be using a health care facility data collection form to show how Fulcrum works.Fulcrum has the most intuitive data collection form builder of any app we've seen. When you design a form Fulcrum calls it an 'app'. Simply drag and drop from the Add Fields section to your 'app' to add questions (see figure below). Available data input types include text, numbers, date, single or multiple choice, photos, videos, and audio.  There are no tricks to collecting GPS locations as with iForm. Fulcrum collects locations automatically.Once a field has been added simply set you parameters. The figure below shows the facility type question being edited. To do this simply click on a field, and fill out the details. It's so easy a 50 year old can do it!The companion mobile app can be downloaded for free from the Apple Store or the Google Play Store. Once installed, login and your data collection app(s) will sync with your mobile device. The figure below shows the health care facilities data collection app on an iPhone. Answering the questions is intuitive. Once collected your data will be synced with your cloud account.Once back in the office, login to your account, select your data collection app, and choose Start Export Wizard. You will be taken to the page below. Choose your file format. A complete array of GIS formats is available including: shapefiles, geodatabases, KML, PostGIS and Spatialite.  Choose any other appropriate options and click Next to download your data.I highly recommend that everyone involved in Community Health Mapping evaluate Fulcrum. Along with iForm and ODK Collect is a CHM recommended data collection tool. There is a monthly subscription fee but it is low. It is the easiest and most flexible tool we've found. You can use the free 30 day trial period to see if it works for you.

Teens Map Environmental Health of Their Community (Sea Islands, South Carolina)

By Guest Blogger: Derek Toth - Communities in Schools CharlestonThe Teen Health Leadership Program (THLP) is in their eight year of existence at St. John’s High School on Johns Island. The program gathers leaders of the school together and focuses on a health topic they feel is affecting their community and assists the community in understanding this topic through the use of media dissemination.  In the past, topics included Autism, Cancer, Stress, Obesity and Alcohol and Drugs and This year, the students wanted to look at their community as a whole with a topic of Environmental Health.The THLP students wanted to see what makes their Sea Island community different.  The Sea Islands are composed of John’s Island, Wadmalaw Island, Seabrook Island and Kiawah Island outside of Charleston, South Carolina.  Students primarily come from John’s and Wadmalaw Islands. These islands are extremely different for many reasons. The students wanted to be able to translate these differences in a new form for the Teen Health Leadership Program. The students were presented with an opportunity to use the Community Health Mapping tools discussed on this blog, and some training made available from the National Library of Medicine. With GIS, the students can pin point differences within the islands for their community to see.(This January Kurt Menke conducted a Community Health Map training at the Medical University of South Carolina College of Nursing.  Two teachers with Communities in Schools Charleston attended and the next afternoon Kurt Menke went to St. John's High School and showed the students how to map their campus with their iPhones.) The students used smart phones, along with an app named iForm, to map points of interest with GPS. They collected well water locations, ground and city water sources, as well as, places in the community to purchase food. The food resources they mapped included farmers markets, produce stands, grocery stores and local farms. The students were able to indicate these points on a map. Google maps was used to create the final map.With the final map they were able to determine that people on Wadmalaw Island have less access to food and water than those on St. John's Island. For example, Wadmalaw Island is limited in places to buy produce or groceries, and has limited access to the farms that John’s Island has. Residents of Wadmalaw Island are on well water, and obtain their produce at the local grocery store on Johns Island, as opposed to driving to one of the many local farms.The final  map was inserted into the Environmental Health project for the community to have a unique perspective of their Sea Island Community. Overall, the students felt that using their smart phones to map their community was easy to learn and fun. They were able to grasp the information quickly and seemed pleased with their results. The group feels it reached it’s goal of accomplishing a fresh look at the Sea Islands and felt it added to their presentation on Environmental Health.

Field Data Collection with iForm

Unfortunately the most recent iOS system update rendered the EPI Collect app unusable. Apparently it is no longer being supported on the Apple platform. With this discovery, and a training in Charleston just around the corner, we set out to find a replacement. We searched for another free app for iPads and iPhones that allows you to develop your own data collection form. Fortunately we discovered iForm  which turns out to be even easier to use, and more robust. (NOTE: It is also available for Android devices.)This app has a lot of similarities with ODK Collect which we recommend for Android users (ODK Collect is described in the Field Data Collection blog post). With iForm you create a free account on the companion iFormBuilder website. You use their online form builder to create your data collection form. The form builder has over 30 different types of data inputs to choose from! For example: text, number, date, time, pick list, phone number, location (GPS coordinates) and images (photographs). Individual data elements can be set up as questions for the data collectors such as: What is the name of the site?Once the form is developed you can begin to collect data.

• Open the app on your mobile device and login.
• Tap the Sync button and all the forms and records that are associated with your account will be downloaded to the device.
• Head out to your project site and collect data.
• At the first data collection site simply open the data collection form, answer each question, and click Done to save the information.
• Repeat at each site.

If you are collecting data while in cellular coverage, the data will be synced to your iFormBuilder cloud account as you go. If you leave cellular coverage that is OK. The on-board GPS receiver on your mobile device will still allow you to collect your locations. Once you are back within cellular range you can Sync your data to your iFormBuilder cloud account. The data can be viewed on the mobile device in tabular or map format. Back in the office the data can be downloaded from the iFormBuilder site in several formats, the most useful of being an Excel spreadsheet. The data in the spreadsheet can then be brought in QGIS or CartoDB and mapped.iForm has some additional features that stream line data collection. You can link your iFormBuilder account to a DropBox or Box account. With this link established your data and photos will be uploaded to a DropBox folder automatically. There are also tools for assigning a form to different users. This allows you to develop one data collection form and share that among a team of data collectors.The free iFormBuilder account has some limits.  You are limited to 10 forms and 100 records per form. However, you can log in to your account, export the data, and delete those online records and continue data collection.In summary, iForm is a powerful and intuitive free app for collecting community health data with iPhones, iPad, and Android devices.

Technology + Youth = Change

by Chad Noble-TabioloIt all started in May 2013 when I watched the documentary entitled Revolutionary Optimists on PBS’s Independent Lens. It showed how young people from a slum in Kolkata, India were able to map the deficient and unsafe water taps in their community, in order to plea with the government for more and safe drinking water lines. The film highlighted technology in an unconventional way. It showed GIS-technology as an innovative tool to mobilize youth for social change.This heralded the beginning of a partnership with Map Your World to develop a mapping project in the Philippines in the summer of 2013. Through coordination with domestic and international partners, the youth mapping program was implemented in Southville 7 — an impoverished and neglected slum community, about three-hours south of metro Manila. The issues faced in Southville 7 ranged from lack of access to jobs, water and electricity to food insecurity and child and maternity health; and because of a lack of response from both the government and non-governmental sectors, the project was aimed to raise awareness and demand change.In just a few weeks, a dozen phones were donated. Youth, ranging from 15 to 23 years old, were trained to go house-to-house to collect data. By the end of three months, 3000 families were surveyed and the needs of the community were mapped. Depicted below is Map 1, which shows the families who have direct access to water in their homes.Because of the unequal distribution of resources, it was evident who had direct access to water and who did not. Map 2 shows those families who did not have direct access to water. These families had to walk more than 1 kilometer to a communal water tap.Lastly, Map 3, represents the top four needs according to the three different subdivisions or sites in Southville 7.  Collectively these maps and data provide an opportunity for proper and adequate planning for public health infrastructure and needs.The Android mobile phones used by the youth were powered by open-source applications for GPS-mapping and data collection. ODK Collect or Open Data Kit was the data collection tool utilized in the project. It can be found on the Android market. (NOTE: This tool is also described in the Community Health Mapping blog post on Field Data Collection). This tool is functional only after uploading a survey form that is created in Microsoft Excel and uploaded to the companion site www.formhub.org. The maps were created online with Map Your World, an online community mapping tool inspired by the Revolutionary Optimists documentary.In the end, the 30 youth involved in the mapping project were able to accomplish an endeavor that many people in their community had not expected. They were able to successfully map who in their community had access to water, electricity, jobs and vaccination for children under five years old, among others. They became leaders who are now equipped with leadership and technological skills that many in their community lack. They were empowered to raise awareness about the social injustices and health inequalities existing among them.The Southville 7’s mapping work was primarily a vehicle for instilling hope, and the use of GPS/mapping-technology offered an opportunity for the youth to be the voice for their community. According to one youth, “For me, mapping is like knowing. Knowing the problems, and how people are coping with them. Through the work we can open the eyes of the people, not only the things that can help them, but things that can help us all.”

Field Data Collection

The workflow covered in the Introduction included three phases: 1) Field Data Collection, 2) Desktop Analysis, and 3) Data Visualization. Here we'll discuss phase 1.We encourage the use of smart phones and tablets for data collection for these reasons:

• Most already have them!
• Many know how to use them
• They're intuitive
• They're portable
• Come with an on board GPS receiver (iPhone 5 uses GPS + GLONASS)
• Have on board cameras
• Can connect to wireless networks
• Access to the internet
• Email is available
• There's an app for that!

Equally as important they are accurate enough for most public health community mapping needs.  For a discussion on their accuracy read this post.There are a myriad of data collection apps available. Part of choosing one comes down to the operating system you are using. We'll cover the three best apps we found for iOS and Android. Our full report and individual user step by step user manuals for each can be found here.iOS (Apple iPhones and iPads)The two best data collection apps for Apples iOS are EpiCollect and GIS Pro. They both allow you to customize the data attributes you collect. One big difference is that EPI Collect is free and GIS Pro, at $299, is the most expensive piece of software we considered in our workflow. However, with that price tag comes a lot of great intuitive functionality.EpiCollect (available for both iOS and Android)To get started with EpiCollect you install the app on your device via Apple's App Store. You then visit the EpiCollect website  and set up a project. Simply give the project a name and design your data collection form. The form can be set up with a variety of attribute columns. For example, feature type, name, description and photo. For most users it takes a practice run to get used to the workflow to set up a data collection form. The second time it goes very smoothly. The project can then be uploaded, via your email address, to your iOS EpiCollect app. Examples of the data collection screen are shown below. On the left is the home screen, on the right is the data collection screen. After data collection, you can sync the mobile app with the website. The data can then be viewed both on the mobile app or on the website. The website also allows for the spatial data to be exported as either an XML or CSV file. Data collected by EpiCollect is limited to point locations. The data can then be brought into a desktop GIS such as QGIS. This will be covered in a future blog post.GIS ProGIS Pro is essentially a lightweight GIS application for iOS. Once purchased a user can have the app on both an iPhone and an iPad. However, each unique user needs their own license. As with EpiCollect, the user can set up custom data collection fields. One additional feature here is that users can collect point, line or polygon (area) data sets within the same project. The data can also be exported in a shapefile format which is then ready to be used by any desktop GIS package. GISPro also allows for sharing of GIS layers. With this feature a team of data collectors can all be working off of the same GIS layer. This is a valuable feature. With the high cost does come great functionality compared to EpiCollect. This was determined to be part of the best workflow and is reviewed more thoroughly in the final report.AndroidIn addition to EpiCollect, the other great app for Android devices is OpenData Kit, known as ODK Collect. The app is free. It is even more intuitive and makes project management even easier than EpiCollect.To get started you will use a companion website called FormHub. Simply sign up for a free account and design your form. Here your data collection form is designed in MS Excel, and a template Excel file makes generating your first form easy. Once designed upload your form and sync your device to your account and you are ready to collect data. On the device the data collection form presents itself as a series of pages for each question.When you are back in range of a network simply sync the app with your account. The data will then be available for download from the website in several formats.SummaryThese are the best apps we found out of dozens reviewed. All three were successfully tested in 2013 by our partners were found to work well. For additional reading download the full report . Step by step user manuals for each can be found here.

How Accurate is the GPS on my Smart Phone? (Part 2)

In Part 1, I introduced the three parts of the hybrid locational system used by tablets and smart phones. Now I'll discuss each individually.Assisted-GPS (A-GPS)A-GPS is by far the most accurate of the three systems on your phone. A-GPS operates a little differently than the typical handheld GPS receiver. The assistance is provided by the cellular network. When connected to a cellular network the smart phone will download data about the GPS satellite constellation. This allows the phone to lock in on a position much more quickly than it could otherwise. The GPS functionality of a smart phone can still be used if the cellular network is unavailable.  However,  when disconnected from a network your phone will take several minutes to hone in on your location, versus just seconds when the network is available.The A-GPS receivers on iPhones have steadily improved from the iPhone 3 to the iPhone 5. In addition to the U.S. DOD GPS system, the Russians have a satellite navigation system called GLONASS. The newest smart phones (e.g., iPhone 4S and iPhone 5) now have GPS chips that use both satellite systems giving increased accuracy!  Europe, India and China are also developing satellite navigation systems and in the not too distant future GPS receivers may be able to use several systems simultaneously and become even more accurate.WiFi and Network PositioningFor any GPS to work the antennae needs a clear view of the sky. Users of smart phones will frequently be in "urban canyons" or indoors. This is where WiFi and cellular network positioning become necessary. Both of these methods are used by smart phones as indoor positioning systems. The phone will use a hybrid approach, using all three methods to locate you. These other two technologies aren't nearly as accurate as A-GPS, but can still locate you sufficiently to find the closest vanilla latte!Generally WiFi positioning is more accurate than cellular network positioning. It uses wireless access points and measures the  intensity of the received signal from one or more networks to find the position. Interestingly it doesn't require your device to be WiFi enabled to work.Cellular network positioning triangulates your position based off of nearby cell phone towers. Phone companies have precise locations for their cell towers, which when combined with signal strength can be used to approximate your location. Both of these techniques are dependent on overlapping signals from either access points and cellular towers. Therefore they're more accurate in urban settings.So What's It All Mean?From numerous tests the typical GPS receiver will achieve an accuracy of 1-5 meters.  Unfortunately assisted-GPS accuracies have not been studied nearly as thoroughly as typical GPS receivers. The best studies to date are those by Dr. Paul Zandbergen at the University of New Mexico. In 2009 he published findings showing that an iPhone 3 had an average accuracy of 8 meters. In that study the error never exceeded 30 meters. Below are the results of his 2009 study including all three locational systems.

• 3G iPhone w/ A-GPS ~ 8 meters
• 3G iPhone w/ wifi ~ 74 meters
• 3G iPhone w/ Cellular positioning ~ 600 meters

Numerous anecdotal studies indicate that the iPhone 4S/5 has become more accurate. In 2011 Dr. Zandbergen tested several Android smart phones. Here he found the accuracies to be slightly better than the 2009 study. They ranged from 5-8 meters. It is likely that the iPhone 4S/5 is within this range as well. It can also be assumed that iPads and other Android tablets will be comparable.Other Options for Increasing AccuracyThere are several third party external GPS receivers that connect to the smart phone via Bluetooth. For example, the Dual 150S can be used to increase accuracy in more remote locations.  It can be worn like a wrist watch, placed on a car dash or strapped to a backpack. It will provide 2.5 meter accuracy and only costs $100.SummaryIf getting within 5-8 meters meets your data requirements smart phones and tablets are a great way to go. If you need greater accuracy you can combine an external Bluetooth GPS receiver with your device and get that accuracy down to the 2-3 meter range. If you require more accuracy than that you will need to invest in a mapping grade GPS receiver.