Antecedent Precipitation Tool (APT)

The Antecedent Precipitation Tool (APT) shows whether rainfall before a field visit was drier than normal, normal or wetter than normal. Ecobot Manager runs the USACE ERDC APT for your sampling points using NOAA weather data, gives you the official PDF report for your deliverables, and can write the result onto your USACE wetland forms. This article shows you how to run an analysis, read the results and add them to your surveys.

To learn about the federal APT method itself, see the EPA's Antecedent Precipitation Tool page. APT in Ecobot is in beta and available on all plans.

Open APT

Open the survey, then select APT in the side menu. APT has three tabs: Configure & Run, Job Status and Results.

Run an analysis

You can run an analysis without checking the survey out. You only need to check it out to add results to your survey forms.

1. On the Configure & Run tab, select the points to analyze. Use the search box and the type, date and state filters to find them.
2. Under Analysis scope, choose how to analyze them (see below).
3. Select Run APT. The button shows how many analyses will run.
4. Check the summary, then select Run.

The summary lists the points, the number of observation dates, the scope, the data source and the estimated time.

Choose an analysis scope

• Single Point (the default): analyzes each point separately, using its own coordinates and observation date. It gives the most detailed, point-by-point record.
• Centroid: analyzes the center of the selected points once, to represent the whole area. Use it for a small site where one analysis fairly represents every point. Give the centroid a name so you can tell several apart. If the points span more than one field date, turn on Create one centroid per field date to run one centroid per date.

Analyze a custom point

A custom point runs APT for a location that isn't one of your sampling points. It's only used for the analysis and doesn't add a point to your survey. It's useful when:

• Your site is coastal, and nearby weather stations don't reflect it well.
• The nearest station is far away or has gaps, and you want to try a different location.
• Your survey covers a large area, and you want to check conditions in one part of it.
• You need to look at a historical or neighboring location that wasn't collected in Ecobot.

To add one, select + Add custom point, enter the latitude, longitude, observation date and type, and optionally a name, then select Add point. It then appears in the list to select like any other point.

If an analysis fails because no suitable weather station is found, a custom point near the survey area can help find a different station.

Follow its progress

After you run an analysis, the Job Status tab opens. It shows overall progress and each analysis's run date, scope and status.

Review the results

The Results tab shows the average score and how many analyses came out drier than normal, normal or wetter than normal. Below that, each result shows its score and condition. Expand a result to see the weather station, Palmer Drought Severity Index (PDSI), season and score breakdown, with PDF and JSON downloads.

Understand the score

APT looks at three rolling 30-day periods before the observation date and rates each one dry (1), normal (2) or wet (3). The ratings are weighted and added to give a score from 6 to 18. Higher means wetter:

A result such as "Normal-12" means a Normal condition with a score of 12. Occasionally a borderline result shows a condition next to a score at the edge of a band. The condition comes from the APT tool itself, and it's what Ecobot writes to your survey.

Download the PDF report

Select the PDF icon on a result to open the official APT report. It includes the observation date, coordinates, elevation, weather station, precipitation graph, 30-year comparison, PDSI, seasonal water balance, and the final score and condition. Include it as an appendix in wetland delineation reports, jurisdictional determinations and permit applications.

Add results to your surveys

Adding a result to a survey sets the point's climatic and hydrologic conditions answer (typical for Normal, atypical for Drier or Wetter) and adds a standard APT sentence to the survey's remarks. Only USACE wetland points can receive results; custom points can't.

1. Check the survey out. If it isn't checked out, select Check out survey on the Results tab.
2. Select Add to survey on a result, or Add to all surveys for every result.
3. Review the summary for each survey. Clear any you want to skip.
4. Select Add to save.

Once added, a result shows Added to survey ✓. If you later edit the survey and the result changes, select that indicator to add it again.

Adding a result only replaces Ecobot's own APT sentence. Anything else you wrote in the remarks stays as it is, even if it mentions the APT. If you run APT again and add the new result, it replaces the old sentence rather than adding a second one. If a point has its own result and also belongs to a centroid, the centroid's result wins.

Change a point's coordinates or date, then run APT again

APT uses each point's coordinates and observation date, which is the point's sampling date. If either one is wrong, correct the point, then run APT again:

1. Check the survey out and open the point. Correct its coordinates with Modify Coordinates, or its Sampling Date, then select Save data. See Edit a point.
2. Open APT. On the Configure & Run tab, the point now needs a new analysis. To list only those points, choose Needs Rerun in the status filter.
3. Select the point, select Run APT, then Run.
4. When the new result is ready, select Add to survey. It replaces the earlier APT answer and sentence on the form.

A point that hasn't changed since its last analysis can't be selected again, because running it again wouldn't change the result.

To change a custom point, select Remove point on its row, then add a new custom point with the right location and date.

If something goes wrong

An analysis stays pending

Refresh the page and check the Job Status tab. If it's still pending, run it again. If it keeps happening, contact Ecobot support.

NOAA services are unavailable

APT relies on NOAA weather and climate data. When NOAA has an outage or is slow, analyses can take longer, stay pending, fail or return no result. Wait a few minutes, refresh the Job Status tab and try again. If NOAA is still down, try later. These outages are outside Ecobot's control.

Not enough nearby weather-station data

Ecobot picks the most suitable weather station by distance, elevation and how complete its records are. Some locations don't have enough nearby station data. Select Retry as gridded to run the analysis with gridded rainfall data instead, which works well for remote sites. You can also try a custom point nearby.

The add buttons don't appear

Check that the survey is checked out to you, that the result is for a USACE wetland point, and, for a centroid, that it has eligible member surveys. If someone else has the survey checked out, the Results tab says who, and you can't add results until they check it in. If every survey already has the current result, there's nothing to add.

Locations outside the US

APT covers the contiguous US, Alaska, Hawaii, Puerto Rico and the US Virgin Islands. Points elsewhere can't be analyzed and are flagged before you run them.

Share feedback

APT is in beta. Select Share APT feedback on the APT page to tell us what's working, what isn't, or what you'd like to see.