This is the main, details page. Given an area bounded by four points these locations can be entered in the app. The app will provide the distance in feet to the designated location, making marker location possible (3 out 4 anyway). Here is shown the South-East corner as the selected marker. The map is limited to approximately 1200 feet but will move with the user. Location, gps, data is only required while the app is being used but it is probably best to close it when not in use to conserve battery. The latitude and longitude for each location (NW, NE etc.) are entered. Once the longitude value is entered both fields will turn green and a marker will be displayed on the screen (if receiving a GPS signal and it is within the field of the map). The distance between the field in green and the user's location is displayed in feet. This app is meant to be used while walking. Pressing the Return key will remove the keyboard. The map can be zoomed in or out. If you want to enter your current location, select a longitude field and click the + icon.
Common to apps using GPS it can take a few seconds or so to get a result. From there the app will display the distance to the corner as the user moves towards or away from the corner. The system seems to be accurate within about 5-10 feet so you will need to look around a little to find any survey marks or geotagged location. Remember you will need to include 4-5 decimal places to achieve this precision. Note 0.0001° latitude is approximately 36 feet (around 37° N). Ref https://www.nhc.noaa.gov/gccalc.shtml with the best accuracy (open sky and multiple satellites) as about 16 feet (https://www.gps.gov/systems/gps/performance/accuracy/). e&oe.
The SAVE page. The current location can be saved, added to the local device database after moving to the Save tab. You can edit entries on this page if necessary. Click the save button to save this location set.
Version 1.2 adds a number of tips in the app. It is possible to save a number of locations sets (up to four points/locations each) to the local device. It is also possible to load/retrieve a location set from the device. Location sets can be edited or deleted. The GPS coordinates for a location can be added to the locations set from the current, your location.
Version 1.3 adds the ability to save multiple Location Sets to the iPhone (files areas) or if connected iCloud (possibly in a folder called "Survey Help"). This Location Sets file in an iCloud folder can be accessed on your Macintosh computer (or iPad) for editing and archiving. Files in a suitable csv format can be placed in the iCloud folder on the computer for access on the iPhone.
The Load page. A location set stored on the device can be retrieved from this page. Here there is one file, A test. Clicking on that green button will load the data for that location set. Multiple locations can be stored on the device. Location sets can be deleted from the device store by swiping left. If an In-App purchase has been completed it is possible to load external location sets, that might be in an iCloud folder. These could be developed in a spreadsheet, such as Numbers, and saved as a .csv file.
MapKit with UIViewRepresentable
LocationManager to find the User
@EnvironObject to allow 'global' variables
CoreData for multiple location sets
StoreKit for the one In-App purchase