Overview
The Antecedent Precipitation Tool (APT) helps determine whether precipitation conditions at a site were drier than normal, normal, or wetter than normal prior to a field observation date.
Ecobot automates the collection and analysis of NOAA weather station data using the Antecedent Precipitation Tool methodology. This analysis helps environmental professionals document site conditions for wetland delineations, permit applications, jurisdictional determinations, and other regulatory reports.
The generated analysis includes a downloadable PDF report that can be attached to project deliverables and regulatory submissions.
*Note: Learn more about the federal Antecedent Precipitation Tool methodology from EPA and the U.S. Army Corps of Engineers: https://www.epa.gov/wotus/antecedent-precipitation-tool-apt
Accessing APT Analysis
From within a Survey, select APT Analysis from the left navigation menu.
Caption: The APT Analysis Configure & Run page displays available sample points, observation dates, coordinates, and analysis settings.
The Configure & Run page displays:
- Available sample points
- Observation dates
- Point coordinates
- Point types (Wetland/Upland)
- Analysis scope settings
Running an Analysis
APT analyses can be run without checking out the survey. However, the survey must be checked out before using the Populate function to save APT results back to survey data.
Step 1: Select Points
Select one or more points using the checkboxes.
Ecobot calculates analyses based on:
- Point location
- Observation date
- Selected analysis scope
Step 2: Choose an Analysis Scope
Use the Analysis Scope dropdown.
Available options include:
Single Point (Default)
Each point is analyzed independently using:
- The point's coordinates
- The point's observation date
This option provides the most detailed point-specific results.
Centroid
Uses:
- The centroid of all selected points
- Each point's observation date
This option can reduce the number of weather station lookups when evaluating larger sites. You can give your centroid a custom name in case you have multiple centroids in your analysis and need to differentiate.
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Step 3: Run APT
Select Run APT.
A confirmation dialog summarizes the request before processing.
Review:
- Points selected
- Unique observation dates
- Analysis scope
- Data source
- Estimated processing time
Click Run Analyses to begin processing.
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Using a custom point
In addition to analyzing existing survey points, you can create a Custom Point for an Antecedent Precipitation Tool (APT) analysis.
Custom points allow you to run an APT analysis without using a survey sampling point. This can be useful when you need weather data from a specific location that differs from your existing survey points.
When to Use a Custom Point
A custom point may be helpful in the following situations:
Coastal Projects
Weather stations near coastlines, bays, estuaries, and barrier islands may be limited or may not accurately represent conditions at your project site.
Creating a custom point allows you to analyze precipitation conditions at a location that better reflects site conditions.
Limited Nearby Weather Stations
In some remote areas, the nearest weather station may be several miles away or have incomplete historical records.
A custom point can help you test alternate locations and identify a better weather station match.
Large Project Areas
For projects spanning a large geographic area, precipitation conditions may vary significantly across the site.
Custom points can be used to evaluate conditions in specific portions of the project area without creating additional survey points.
Historical Site Evaluations
You may need to evaluate antecedent precipitation conditions for a location that was not originally collected in Ecobot.
Custom points allow you to analyze historical observation locations without modifying survey data.
Reviewing Adjacent Properties
When evaluating hydrologic conditions near a project boundary, mitigation site, or reference area, a custom point can be used to compare precipitation conditions at nearby locations.
Note: Custom points are used only for APT analysis and do not create survey sampling points within your project.
Tip: If an APT analysis fails because suitable weather station data cannot be located, creating a custom point near the project area may help identify a different weather station and allow the analysis to complete successfully.
Monitoring Analysis Progress
After submission, Ecobot automatically switches to the Job Status tab.
The Job Status page displays:
- Pending analyses
- In-progress analyses
- Completed analyses
- Batch progress
Analysis Complete
Completed analyses include:
- Antecedent Score
- Condition
- PDSI Classification
- Season
- Analysis Scope
Reviewing Results
Select the Results tab to review completed analyses.
The Results page includes:
Summary Metrics
- Average score
- Number of Drier than Normal analyses
- Number of Normal Conditions analyses
- Number of Wetter than Normal analyses
Point-Level Results
Expand a result to view:
- Antecedent Score
- Hydrologic Condition
- Weather Station
- PDSI Drought Index
- Seasonal Classification
- Score Breakdown
- PDF and JSON downloads
Adding Results to Surveys
APT results can be added directly to survey records.
- Add to Survey updates an individual survey point.
- Add to All Surveys updates all applicable survey points from the analysis.
- You can deselect certain points from being appended when selecting all.
Note: The survey must be checked out before using either option.
Before saving, Ecobot displays a confirmation screen showing the precipitation summary that will be added to each survey.
Review the proposed updates and select Add to Surveys to save the results.
Downloading the PDF Report
Each completed analysis includes a View PDF Report option.
Go to Results > PDF icon next to the point
The generated PDF includes:
- Observation date
- Site coordinates
- Elevation
- Weather station information
- Antecedent precipitation graph
- 30-year precipitation comparison
- Palmer Drought Severity Index (PDSI)
- Seasonal water balance information
- Final antecedent score and condition
Example report outputs include NOAA precipitation comparisons, weather station selection details, and final scoring. The report can be included as supporting documentation in wetland delineation reports and permit submissions.
*Best Practice: Include the APT PDF report as an appendix in wetland delineation reports, jurisdictional determinations, and permit application packages.
Understanding APT Results
APT evaluates precipitation conditions across three rolling 30-day periods prior to the observation date.
Each period receives a classification value:
| Condition | Value |
| Dry | 1 |
| Normal | 2 |
| Wet | 3 |
These values are weighted and combined to calculate a final antecedent score.
Result classifications generally fall into the following categories:
| Classification | Score Range |
| Drier than Normal | Less than 10 |
| Normal Conditions | 10–14 |
| Wetter than Normal | 15 or greater |
These classifications provide context for hydrology observations and help support wetland determinations.
Troubleshooting
Analysis Remains Pending
If an analysis remains pending longer than expected:
1. Refresh the page.
2. Check the Job Status tab.
3. Retry the analysis.
If the issue persists, contact Ecobot Support.
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NOAA Services Are Unavailable
APT relies on external NOAA weather and climate datasets.
Occasionally NOAA services may:
- Experience outages
- Become temporarily unavailable
- Return incomplete data
- Time out during processing
When this occurs:
- Analyses may take longer than expected
- Requests may remain pending
- Processing may fail
- Results may not be returned
Resolution
1. Wait several minutes.
2. Refresh the Job Status page.
3. Retry the analysis.
4. If NOAA services remain unavailable, try again later.
*Warning: NOAA outages and weather service interruptions are external dependencies and may impact APT processing availability. These interruptions are outside of Ecobot's control.
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No Nearby Weather Station Found
Ecobot automatically selects the most appropriate weather station using:
- Distance from the site
- Elevation similarity
- Data completeness
In rare situations, insufficient weather station data may prevent an analysis from completing successfully. If this occurs, retry the analysis later or contact Ecobot Support.
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Submit Feedback
APT Analysis is currently in Beta.
Use the feedback form to share:
- Feature requests
- Workflow improvements
- Processing concerns
- Data quality feedback
Your feedback helps improve future releases.
FAQs
What is the APT?
The Antecedent Precipitation Tool analyzes the precipitation record near a location for the period before your survey and classifies it as Drier than Normal, Normal, or Wetter than Normal. Ecobot runs it for you and can write the result onto USACE wetland forms.
Are the results official?
The determinations come from the USACE/ERDC Antecedent Precipitation Tool. Ecobot shows the version in use with a link to the source tool, and each analysis includes the official PDF report.
Does running APT change my survey data?
No. Running an analysis only produces a determination. Your survey forms aren't changed until you explicitly apply a result and confirm.
Which surveys can APT results be applied to?
Only USACE wetlands survey points. Other form types and custom (ad-hoc) points are skipped.
Is there a cost or limit to running analyses?
APT in Ecobot is currently in beta and available on all plans.
Running an analysis
What's the difference between single point, centroid, and custom point?
Single point runs APT separately for each selected point. Centroid computes the center of the selected points and runs one analysis for the area; those points become its "members." Custom point analyzes an ad-hoc lat/long that isn't one of your survey points.
When should I use a centroid instead of single points?
Use a centroid for a small observation area where one analysis fairly represents the whole site — it saves running APT on every point. Use single points when points may have genuinely different conditions or you want a per-point record.
What does "Create one centroid per field date" do?
If your selected points span multiple field dates, it submits a separate centroid for each date, each computed from that date's points. The field date is appended to each centroid's name automatically.
How long does an analysis take?
It varies by location and data source. The confirmation dialog shows an estimated total time based on recent runs, and the Status tab updates as each one finishes.
Does it work outside the US?
APT covers U.S. regions: CONUS, Alaska, Hawaii, Puerto Rico, and the U.S. Virgin Islands. Points outside those regions can't be analyzed and are flagged before submission.
Why did my analysis fail with "not enough nearby weather-station data"?
That location doesn't have enough nearby weather stations for a standard (station-based) analysis.
What is "Retry as gridded"?
A re-run that uses gridded rainfall data instead of weather-station data. It's the fix for "not enough nearby station data" failures and works well for remote sites with sparse station coverage.
Reading results
What do the score and condition mean?
The condition (Drier / Normal / Wetter) is the classification. The score (about 6–18) is a weighted index of the recent precipitation windows — higher means wetter.
What are the score bands?
As a guide: ≤ 8 → Drier, 9–12 → Normal, ≥ 13 → Wetter.
What does a token like "Normal-12" mean?
It's the condition and score together — condition "Normal" with score 12.
Can the condition and the score band ever disagree?
Occasionally. The condition is the APT tool's own classification, while the score is a separate weighted index — so a borderline case can show a "Normal" condition next to a score at the edge of a band. The written result follows the condition.
Where is the official PDF report?
The PDF icon on each completed result row opens the official APT report.
Applying results to surveys
What does applying actually change on my survey?
Two things: it sets the climatic / hydrologic conditions answer (typical for Normal, atypical for Drier or Wetter), and it appends a standardized APT sentence to the survey's remarks.
Why do I have to check out the project to apply?
Applying writes to survey data. Checking out prevents your changes from being overwritten by data syncing from a field device, and signals to teammates that the project is in use.
How do I check out the project?
From the Results tab action bar, click Check out project — it checks out in place and the apply controls unlock immediately.
What if someone else has it checked out?
The action bar shows Checked out by <name> and applying is blocked until they check it back in.
Can I run analyses without checking out?
Yes. Running and reviewing don't require checkout — only applying does.
Can I apply to just some surveys instead of all of them?
Yes. The confirmation dialog lists each affected survey with a pre-checked checkbox — uncheck any you want to skip, and only the checked ones are written.
What does "up to date" mean in the apply dialog?
That survey already has the current result, so it won't be re-written.
What does "Added to survey ✓" mean?
The current APT result is present on that survey. For a centroid it shows Added to N surveys ✓ when all member surveys carry the centroid's result.
I edited my survey and the APT result is gone / wrong — how do I restore it?
Click the Added to survey ✓ indicator — it's clickable and re-opens the apply dialog showing exactly what will be restored.
Will applying delete my own remarks or notes?
No. Applying only ever replaces the standardized APT sentence. Any text you wrote before or after it is preserved.
What if my own notes mention "the USACE Antecedent Precipitation Tool"?
They're safe. Ecobot only replaces text that exactly matches its own generated sentence (a very specific pattern), not free text that merely mentions the tool.
Could I end up with duplicate APT sentences?
Not from normal use — each apply replaces the previous APT sentence. The only way to get two is to hand-edit the auto-generated sentence so Ecobot no longer recognizes it; then a fresh one is appended rather than risk deleting your edit. Even then, nothing you wrote is lost.
What if I re-run APT and the result is different?
Applying the new result replaces the old APT sentence in place and updates the conditions answer. No duplication.
A point is part of a centroid AND has its own single-point run — which wins?
The centroid wins. Applying the centroid overwrites that member's individual APT sentence with the centroid's determination.
Centroids
What is a centroid, exactly?
The geographic center of the points you selected. APT runs once at that center to represent the whole area.
Why would I name a centroid?
So you can tell multiple centroids apart. A project can contain several (one per area, or one per field date); without names they'd all look the same. The name is required and pre-filled with "Site Centroid."
What are "member surveys"?
The survey points you selected to build the centroid. Applying the centroid writes its result to those member surveys.
The centroid has 3 members but only offers "Add to 2 surveys" — why?
One eligible member already has the current result ("up to date"), so only the remaining two need it. The count reflects surveys that would actually change.
I added a custom point as a centroid member — does it get the result?
No. Custom points aren't real survey forms, so they aren't written to and aren't counted toward the centroid's member total.
Troubleshooting
The apply buttons aren't showing on a row.
Check that (1) the project is checked out by you; (2) the row is a USACE-wetlands point (custom points don't get the action); and (3) for centroids, that it has eligible member surveys.
I just ran or applied something but the screen looks out of date.
Reload the page. A fresh load always reflects the latest state.
An analysis keeps failing.
If it's "not enough nearby station data," use Retry as gridded. For other errors, the failure reason is shown on the Status tab; if it persists, send feedback with the point's coordinates and date.
Nothing happened when I clicked "Add to all surveys."
If every eligible survey is already current, there's nothing to write — the dialog says so and the confirm button reads "Nothing to add."