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Western Dam Engineering <br /> Technical Note <br /> <br /> May 2016 <br /> <br />3 <br />satellites more rapidly. There is a good article on this <br />for those who wish to understand more: A-GPS Versus <br />GPS [2]. <br />Recent creative marketing has caused some confusion <br />on the topic by marketing tablets with “aGPS”, which <br />essentially means “No GPS”, but when connected to <br />Wi-Fi, the network IP address can approximate the <br />device’s location. <br />Cautions <br />Mobile apps are not typically used for design-related <br />tasks, but can be useful to engineers in various field <br />and day-to-day tasks. As with all engineering tools, it is <br />important to understand the underlying theory behind <br />the technology and its related limitations. Understand <br />the qualifications of the developer and efforts made to <br />validate or calibrate the app. Almost all apps have <br />revised versions, which in some cases were introduced <br />to correct errors found by users. This article is not an <br />endorsement of any application, nor confirmation of <br />its accuracy. The brief descriptions here are intended <br />to introduce the reader to these tools; however, <br />describing the technical theory behind each app or <br />explaining its proper technical use is beyond the <br />practical scope of this article. But the authors have <br />experimented with most of the apps presented and <br />offer some relevant commentary. <br />Field Inspection Applications <br />In earlier times, engineers wore thick leather belts <br />because besides holding their pants up, the belt had to <br />carry a flashlight, GPS unit, Brunton Compass, tape <br />measure, camera, hand level, calculator…. Now, that <br />same belt load may be reduced to a phone or tablet. <br />Maps and Orientation <br />Map applications are probably the most commonly <br />used. <br />Google Maps (Google, Inc., Android/iOS, Free): <br />Map apps require internet connectivity via cellular <br />data or WiFi to operate efficiently. However, they can <br />also be used offline if the maps are downloaded ahead <br />of time and the device has a GPS chip. Google Maps <br />has such broad capabilities that it is difficult to <br />summarize; however, most readers are already familiar <br />with this powerful tool. For dam engineering related <br />tasks, map applications provide directions to the dam <br />site, measuring tools to estimate rough proximity of <br />various features, and satellite imagery. Satellite <br />imagery is especially useful to visualize areas within <br />the downstream flood plain, the condition of the <br />contributing watershed, and proximity of upstream <br />dams and control structures. Its easy operation and <br />power make this one of the most commonly used <br />apps. Google Maps is available for free on both <br />Android and iOS devices. Apple has developed Apple <br />Maps, but it does not offer the same features of the <br />competition. CNET published an article comparing <br />available offline navigation apps: Offline Navigation <br />Apps [5]. <br />Back Country Navigator (CritterMap Software LLC, <br />Android, $11.99): <br />Backcountry Navigator is another useful mapping <br />application that provides offline topographic maps <br />geared more to…yes…back country areas. It also <br />includes a compass and tracking statistics. It requires <br />upfront work to get familiar with the interface, but <br />provides many useful tools. One feature that makes <br />this app stand out is the large availability of map <br />sources that can easily be downloaded and used once <br />outside of cell coverage. This includes quality <br />international maps. It is worth spending the time <br />reading the help screens to understand how and <br />where these downloaded files are stored, as it is not <br />intuitive. This app also can be used in a fashion that <br />minimizes battery use, a large benefit as navigational <br />and mapping apps are notorious battery hogs. <br />Theodeolite (Hunter Research and <br />Technology, iOS, $5.99): <br />Similar to Backcountry Navigator, the Theodeolite app <br />is a map application that provides a compass, two-axis <br />inclinometer, rangefinder, GPS, altimeter, topographic <br />maps, and tracker. The app also allows location-tagging <br />of photographs, which can be useful for field <br />inspections. Some features require data connectivity <br />but most aspects of the application require only the <br />connectivity associated with the device’s GPS.