GPS for Dummies.pdf - Engineering Surveyor

Chapter 3: GPS Fundamentals61Figure 3-4:Simple andsophisticatedGPSreceiverscreens.Some GPS receivers have maps that show roads, rivers, cities, and other featureson their screens. You can zoom in and out to show different levels ofdetail. The two types of map receivers are Basemap: These GPS units have a basemap loaded into read-onlymemory that contains roads, highways, water bodies, cities, airports,railroads, and interstate exits.Basemap GPS receivers aren’t expandable, and you can’t load moredetailed maps to the unit to supplement the existing basemap. Uploadable map: More detailed maps can be added to this type of unit(in either internal memory or an external memory card). You can installroad maps, topographic maps, and nautical charts. Many of these mapsalso have built-in databases, so your GPS receiver can display restaurants,gas stations, or attractions near a certain location.Chapter 9 covers features and how to use GPS receiver manufacturermapping programs to upload maps to your GPS unit.Refer to Figure 3-4 to see screens from a GPS receiver with a simple plot mapand another GPS unit with an uploadable map.GPS receivers that display maps use proprietary map data from themanufacturer. That means you can’t load another manufacturer’s orsoftware company’s maps into a GPS receiver. However, clever hackersreverse-engineered Garmin’s map format. Programs on the Internet cancreate and upload your own maps to Garmin GPS receivers; GPSmapper ispopular.A handheld GPS receiver’s screen is only several inches across. The limitationsof such a small display certainly don’t make the devices replacementsfor traditional paper maps.