GeoMattix

7 Good Habits for Collecting Quality GPS Data

Fri, 12 Jul 2019 22:21:59 -0700

You’ve bought your GPS equipment and you’re ready to start collecting data for your GIS. That’s great! But before you dive in and do something foolish, take a moment to learn how you can prepare yourself to collect good, quality GIS data you’ll be proud to hand off.

1. Understand how GPS works. How do all of those satellites up in the sky tell you your XY location? What is differential correction? Does GPS work on a cloudy day? Before you go out and try to collect GIS-ready data, educate yourself about how the GPS system works.

Knowing how the system works will help you work WITH your equipment. You will understand what the GPS settings in your field software mean and how to do basic things like turn on or off SBAS, check your DOP values, and ensure your almanac is current.

Today’s GPS equipment is easy enough for anyone to use without knowing a thing about the GPS system, but if you want to collect quality field data, educate yourself first.

2. Design a field-friendly workflow. Many GPS software packages highlight the ease with which you can take your GIS out into the field. And it’s true, it is easy. But it’s not always recommended.

Your office GIS probably has functionality that simply isn’t suited for field work. Things like attributes in your feature classes that describe the proper placement of labels, related tables that give access to esoteric information, a scale that covers hundreds of square miles, among others.

At best, much of this is simply not necessary in the field. At worse, taking a complex GIS into the field on a mobile GPS unit can result in poor performance and frustrated field workers. Unless you are using a laptop or Windows tablet in the field and don’t mind wading through more data than necessary, you will have to simplify your GIS data first.

Design a solid workflow for how you will move from office GIS...Read More

Using the Select Features Tool in ArcMap

Tue, 02 Jul 2019 21:48:39 -0700

Selecting Features in ArcMap

Of all the methods for selecting features in your GIS, the Select Features tool is by far the easiest. With little training, you can begin happily clicking away at your map, turning your features cyan blue – Esri’s default color for selected features. With a little bit of training, you can command the Select Features tools to do amazing things.

A Few Tips Go a Long Way

In this video, Michele GeoMattix shows you a few tips and best practices for using the Select Features tools in ArcGIS for Desktop.

Make a Series of Maps Using Data Driven Pages

Tue, 02 Jul 2019 21:46:22 -0700

Creating a Series of Maps

Have you tried using data driven pages yet? It was released with version 10 of ArcGIS for Desktop and it makes the process creating a map book so much easier. A good example is a river feature. Making one map for a single, long river will not show enough detail for most practical applications. Using data driven pages allows you to specify the length along the river you want each map to portray – say 2 miles – and then it creates a series of maps each showing a different 2 mile stretch of the river.

Create a Strip Map Index for Line Features

You may have a polygon layer — say counties — that you want to define the extent of each of your maps. If you do not, then you can use the Strip Map Index Features geoprocessing tool. From there, you simply set up your data driven pages and ArcMap will do the work for you.

In this short video, I show you it’s done from start to finish.

Find Hotspots in your GIS Data

Tue, 02 Jul 2019 21:43:50 -0700

Find Hot Spots in Your Data

Does the thought of working with spatial statistics in GIS send shivers up your spine? Rightfully so for some of the statistics tools. But not for the Optimized Hot Spot Analysis tool. It’s an easy to use tool that generates an output feature class complete with an already-symbolized layer. The layer’s symbology is color coded based on statistically significant hot and cold spots in your data.

What is a Hot Spot?

A hot spot is a cluster of high values and a cold spot is a cluster of low values. The ‘values’ in this case can be simply the XY location of the points or polygon centroids. This would be the appropriate choice for, say, locations of crime. The results would show hot spots of crime activity. Alternatively, if your data contain an attribute field with concentration or intensity values, you can use that field as your analysis field. The results would show hot and cold spots of concentrations. An example would be lead concentrations in soil samples. You are not interested in the locations of the soil samples but rather the lead concentration values.

How Do I Use It?

Esri has made it very easy to perform a hot spot analysis with the Optimized Hot Spot Analysis tool. The tool looks at your data and presets most of the parameters for you – unlike the regular Hot Spot Analysis tool which requires you do the heavy prep work yourself. I suggest using the Optimized Hot Spot Analysis tool if and until you are comfortable doing the heavy lifting yourself. In the video below, I’ll show you how to use this tool and a few tips and tricks for working with the results.

ArcGIS Overlay Tools

Tue, 02 Jul 2019 21:41:12 -0700

Overlay Tools

As a GIS instructor, I always tell my students that its much easier to SEE what the overlay tools do rather than try and describe them. They are very powerful tools that combine two or more feature classes into a new feature class. The new feature class picks up all of the attributes of the input feature classes.

Specific GeoProcessing Tools

There is no single tool called “overlay.” Rather, the overlay toolset which is in the Analysis toolbox in ArcToolbox, contains various overlay tools. In the video, below, I will show you three of them: Intersect, Union, and Erase.

Create a GIS Study Area Polygon

Tue, 02 Jul 2019 21:38:04 -0700

Where to Begin a New GIS Project?

For just about every GIS and GPS project I’ve worked on, one of the essential ingredients is a polygon that defines the boundary of the study area. I quickly learned that this is the best place to begin when gathering data for a new project.

Why Do You Need a Study Area Polygon?

I can think of three good reasons why you need a study area polygon:[red_tick_list width=”100%”]

Use it as the cookie-cutter shape to clip all of your other project data down to size.
Know the area and perimeter distance of your study area.
Provides a manageable extent to work with for a new GPS data collection project so your mobile map has more than just a white screen zoomed out to the extent of the coordinate system.

How to Create a Study Area Polygon

If your study area follows political boundaries such as a county, country, or census tract, then all you have to do is select the boundary and export it to a new feature class. For more fine tuned boundaries, you will probably have to use the ArcGIS for Desktop editing tools to specify exact coordinates, follow land features, and do whatever is required to define your polygon.

I discovered a way to define a general study area polygon that requires no editing whatsoever. Is it quick? Yes. Is it crude? Yes. Will it work for every situation? Probably not. Whether it works for your current GIS project, or not, is for your to decide. Either way, it’s a good trick to have in your GIS arsenal.

Enjoy!

Geocoding in ArcMap

Tue, 02 Jul 2019 21:32:51 -0700

From Address to XY Coordinate

I spent a lot of time at the post office this past holiday season. Each time I gave a package to the teller, he or she would enter the address into the computer to make sure it was valid – essentially a form of geocoding.

Geocoding is the GIS process of converting a street address into an XY coordinate. Since GIS stores data as XY coordinates, geocoding is extremely useful for converting lists of addresses into GIS features, thereby bestowing the power of GIS onto your data. Locations of customers, crime events, and delivery routes are a few examples where geocoding comes in handy.

What You Need to Geocode an Address

Traditionally, there are three things you need to geocode:

A valid address
Street data properly attributed for geocoding
Address locator – a series of definitions and rules that tell the software how to use the street data to find the address

Some organizations maintain their own street data and devise their own address locators. If your organization doesn’t do this, never fear. Esri has tools that you can use for free to geocode individual addresses as well as lists or tables or multiple addresses.

One method calls upon the ArcGIS Online services that are integrated with ArcMap – Esri provides the data and the address locator through their web service.

The second method I will show you uses the Esri Streetmap data that is included with the Esri Data and Maps which you can download from your MyEsri.com account, provided you are an ArcGIS Desktop customer. Here, Esri provides the street data and the address locator which is stored on your computer.

Working with Length in GIS Attributes

Tue, 02 Jul 2019 21:28:03 -0700

Length Attribute Field…or Not

When you open a feature attribute table for line data in ArcGIS for Deskop, you might see a LENGTH field and you might not. Why the inconsistency? It has to do with the format of your feature class. Geodatabase line feature classes include a system defined attribute field that stores the length of each feature; shapefiles do not.

But My Shapefile DOES Have a Length Field

Some shapefiles do have a length field, it’s true. But they are not system- defined attribute fields. System-defined attribute fields are ones that the software creates and manages. You can read the values, but you cannot edit them.

If your line shapefile includes a length field, it’s because someone added it, either manually or by using some third-party tools. It is a user-defined attribute field. The lengths can be calculated and added to the attribute table, but there is no dynamic link between the features and length attribute value. That means that if you edit a line feature and change its length, the length attribute value will not be recalculated automatically as it is with the system-defined attribute field.

What Units Are the Lengths In?

The geodatabase system-defined length attribute field displays lengths in the linear unit of the coordinate system of the feature class. If, for example, your line feature class is in UTM coordinates, then the length values will be in meters because meter is the linear unit of the UTM system.

Can I Change the Units?

Yes, you can change the units of the system-defined length values. Well, sort of. You can add a new attribute field and use it to store length values that are based on the system-defined length values.

I’ll show you how in this video.

Get Free GIS Data from Esri

Tue, 02 Jul 2019 21:22:51 -0700

Need Some Basic GIS Data for Your Project?

Country boundaries, U.S. states, counties, interstates, federal lands… So much GIS data is yours for the downloading. And directly from Esri. So you know it’s good, right?

Esri Data and Maps

If you are a long time Esri GIS user, you may recall that Esri Data and Maps CDs that came in the folder with your ArcGIS installation CDs. It was very easy to install the Data and Maps then.

Several years ago, Esri switched to a download model where users must log on to their my.esri.com account to access and download software they have purchased or are otherwise entitled to.

The Data and Maps is not longer so easy to locate. Plus, the download file is HUGE. Most users don’t even know that this data exists.

Download the Whole Data and Maps Set

If you can get into your my.esri.com account, you’ll find the Data and Maps under the “additional products” link for ArcGIS for Desktop v10.3. The Data and Maps link does not appear under every version, so take care to click on 10.3 which is the current version as of this posting.

Download Layer Package by Layer Package

If you do not have access to my.esri.com, or you can’t download the large file, don’t despair. You can download the datasets one by one, as needed, from ArcGIS Online.

I’ll show you how in this video.

Collector for ArcGIS & Scale Dependency

Tue, 02 Jul 2019 21:19:57 -0700

Esri’s Collector App

Have you tried using Esri’s Collector app for GPS fieldwork yet? For the most part, it works like a charm and is the simplest Office-to-Field-to-Office workflow I’ve seen yet. Recently, however, I encountered a problem that nearly sank one of my project.

Scale Dependency on Your GIS Layers

Esri recommends setting scale dependency on your layers before sharing your map as a service. As part of the Collector workflow, I set scale dependency on a few of my layers for which I have existing features. This helps improve the performance of the service as you pan and zoom around your web map.

The Problem

In Collector, if you are not zoomed to the visible scale range of your scale-dependent layer(s) then the layers will not appear as collectable when using the Collect New Feature tool. It gives the impression that those layers are simply unavailable for collecting new features.

Once zoomed in to the visible scale range, the layers do appear as collectable. There is no visual indication of scale-dependency in Collector as there is in ArcMap and ArcGIS Online. If the field crew is not familiar with your Collector project’s settings, they may assume that the project isn’t working properly.

Let Me Show You…

In the video below, I’ll show you the problem and offer a suggestion for how to avoid it.