Demo Iteration Project: Difference between revisions
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{{technical|type=section}} | |||
{{demo project summary | {{demo project summary | ||
| title=Demo Iteration | | title=Demo Iteration | ||
| demographic=hydrologists and other water experts | | demographic=hydrologists and other water experts | ||
| showcases=the rainfall overlay in a iteration mode | | showcases=the rainfall overlay in a iteration mode | ||
| image= | | image=Demo_iteration.jpg | ||
| description=The demo | | description=The demo showcases the [[Simulation Core|iteration]] functionality for adjusting ground infiltration speed via a combo formula. | ||
}} | }} | ||
| Line 10: | Line 12: | ||
The demo project simulates a Dutch polder to demonstrate how rainfall infiltration can be modeled using the [[Simulation Core|iteration]] option. | The demo project simulates a Dutch polder to demonstrate how rainfall infiltration can be modeled using the [[Simulation Core|iteration]] option. | ||
We want the speed at which rainwater infiltrates to depend on the degree of saturation of the soil. | We want the speed at which rainwater infiltrates to depend on the degree of saturation of the soil. Dividing the rain event into multiple iteration steps allows the infiltration rate to be adjusted based on soil saturation, increasing calculation accuracy. | ||
The purpose of this demo project is to clarify how an iterative calculation can be made. In this case, the infiltration of water during and after a precipitation event was chosen. | The purpose of this demo project is to clarify how an iterative calculation can be made. In this case, the infiltration of water during and after a precipitation event was chosen. This demo project can also serve as a basis for performing other iterative calculations. | ||
==Setup of the Demo Project== | ==Setup of the Demo Project== | ||
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===Combo Surface U and Combo Surface V=== | ===Combo Surface U and Combo Surface V=== | ||
These overlays | These overlays define the initial surface water velocity in the X and Y directions. For water flowing down a slope, the final velocity of one iteration step becomes the initial velocity for the next. The input grid is the result of the last calculation. The formula ensures calculations use data from the previous time step, except for step 0, where a value of 0 is used. | ||
Make sure to check the box "previous" to make sure the [[Combo Overlay]] uses the U and V of the previous | Make sure to check the box "previous" to make sure the [[Combo Overlay]] uses the U and V of the previous iteration step.<br> | ||
The formula in the combo overlay should in this case read: <code>IF(EQ(ITERATION, 0), 0, A)</code> | The formula in the combo overlay should in this case read: <code>IF(EQ(ITERATION, 0), 0, A)</code> | ||
===Combo Fraction and Combo Groundwater Depth=== | ===Combo Fraction and Combo Groundwater Depth=== | ||
Combo Fraction and Combo Groundwater Depth use input from the previous iteration step, unless it is step 0. In that case, a [[Global]] value is used. The [[Global]] DEFAULT_FRACTION is used for the saturation percentage, and the global DEFAULT_TABLE is used for the groundwater level. | |||
<br> The formula in the combo overlay Combo Fraction should in this case read: | <br> The formula in the combo overlay Combo Fraction should in this case read: | ||
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When setting the rainfall overlay, the default settings can be used. The exceptions are described below. | When setting the rainfall overlay, the default settings can be used. The exceptions are described below. | ||
Rain Event Duration: | Rain Event Duration: Specifies the total calculation duration, which is subsequently divided into iteration steps. | ||
<br>Water System – Water Level: Here the initial water level and the U and V flow are set. Use the option "Advanced: Select Grid | <br>Water System – Water Level: Here the initial water level and the U and V flow are set. Use the option "Advanced: Select Grid overlay to set initial water level and also flow UV". | ||
The water level is set based on a specific overlay, which is the combo | The water level is set based on a specific overlay, which is the combo overlay Surface. Similarly, the y and x speed from the combo overlay is used as initial input. | ||
<br>Groundwater: Initialize the groundwater level using the Groundwater Depth combo overlay. | <br>Groundwater: Initialize the groundwater level using the Groundwater Depth combo overlay. | ||
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==Iteration Collector== | ==Iteration Collector== | ||
The [[Iteration Overlay|Iteration Collector]] is a type of overlay. It shows the results of each iteration step. An iteration collector needs an input overlay, in this case it is the Rainfall overlay. One timeframe is saved for each iteration step. | |||
Modulus | The [[Iteration Overlay#Modules|Modulus]] attribute of the Iteration Collector determines how many iterations are stored. By default, this is set to 1. This means that only one (the last) result of each iteration step is saved and used as a timeframe in the iteration collector. When the modulus is set to 1, every iteration is stored. When you set the modulus to 2, half of the iteration values are stored. | ||
==Indicator== | ==Indicator== | ||
The indicator sets the start and end times for the rainfall overlay iteration steps. It uses queries like <code>SELECT_ITERATIONS_WHERE</code> and <code> SELECT_ATTRIBUTE_WHERE_NAME_IS_RAIN_M_AND_OVERLAY_IS_10_AND_RELATION_IS_WEATHER_AND_INDEX_IS_2</code> to determine the number of steps and total simulation time. The <code>UPDATE_OVERLAY_PARTIAL_START_SEC_WHERE_OVERLAY_IS_3</code> and <code>UPDATE_OVERLAY_PARTIAL_END_SEC_WHERE_OVERLAY_IS_3</code> queries then adjust the timing for the next step, identified via <code>SELECT_ITERATION_WHERE</code>. Fraction Start and End define these as fractions of the total simulation time. | |||
==Number of Iterations== | |||
Set the number of iterations in the [[calculation panel]] under the 'iteration' option. This is set to 1 by default. | |||
== | ==Exploring the results== | ||
To view the results, play back the iteration sequence. The following results can be seen here: | |||
* Water on ground level in meters | |||
* Iteration Fraction: The fraction of the total water storage capacity of the unsaturated zone that is filled with water in meters | |||
* Iteration Storage: The amount of water in the unsaturated zone in meters | |||
* Iteration Infil Speed: The infiltration speed in meters per day | |||
* Iteration Rain: The total amount of rainfall up to that point in the simulation in meters. | |||
* Iteration ground table: The groundwater level in m + datum. | |||
When the iteration Infil speed is viewed, it becomes clear that the two different soil types (BOFEK IDs) give a different result in the infiltration speed. | |||
==Notes and Limitations== | ==Notes and Limitations== | ||
Debugging cannot be downloaded per iteration but can be saved for each iteration. | Debugging cannot be downloaded per iteration but can be saved for each iteration. | ||
Specific updates (e.g., updating attributes for certain building types in iteration 5) can be executed using the API and indicator but not through TQL for non-initial iterations. | Specific updates (e.g., updating attributes for certain building types in iteration 5) can be executed using the API and indicator but not through TQL for non-initial iterations. | ||
===Effect of Iterations on Calculation Accuracy=== | |||
== | When calculating a precipitation event, there may be a difference between a standard calculation and an iterative calculation, even if they use the same rainfall overlay. This is due to the way data is processed during an iterative calculation.<br> | ||
In a standard calculation, the precipitation event is executed in a single step. In an iterative calculation, on the other hand, the event is split into multiple time steps, for example 10. After each iteration step, the data is stored and prepared for the next step. Rounding occurs during this process, which can affect the accuracy of the results.<br> | |||
The water levels are stored internally in a 64-bit format, which provides high precision with 12 decimal places. However, the results are displayed in a 32-bit format, which has an accuracy of 6 decimal places. In the iterative calculation, the 32-bit result is used. This causes small rounding differences between the results. The more iteration steps there are, the more often this rounding occurs and the larger the deviation can become.<br> | |||
These rounding differences are minimal. If required, additional measures can be implemented to further increase precision. | |||
{{article end | {{article end | ||
Latest revision as of 11:36, 14 July 2026
The Demo Iteration project is available for all users and can be found in the main menu under Edit projects. This project does not count towards your license.
This project is intended for hydrologists and other water experts.
This project showcases the rainfall overlay in a iteration mode.
The demo showcases the iteration functionality for adjusting ground infiltration speed via a combo formula.
Calculations using the Iteration option
The demo project simulates a Dutch polder to demonstrate how rainfall infiltration can be modeled using the iteration option.
We want the speed at which rainwater infiltrates to depend on the degree of saturation of the soil. Dividing the rain event into multiple iteration steps allows the infiltration rate to be adjusted based on soil saturation, increasing calculation accuracy.
The purpose of this demo project is to clarify how an iterative calculation can be made. In this case, the infiltration of water during and after a precipitation event was chosen. This demo project can also serve as a basis for performing other iterative calculations.
Setup of the Demo Project
The demo project consists of a number of components that are essential for this calculation.
Combo Overlays
Before we create the Rainfall event, a number of overlays are created that serve as input for the various iteration steps. At the end of each iteration the combo overlay is updated an serves as the input for the next iteration step. We'll go through the different combo overlays.
Combo Surface U and Combo Surface V
These overlays define the initial surface water velocity in the X and Y directions. For water flowing down a slope, the final velocity of one iteration step becomes the initial velocity for the next. The input grid is the result of the last calculation. The formula ensures calculations use data from the previous time step, except for step 0, where a value of 0 is used.
Make sure to check the box "previous" to make sure the Combo Overlay uses the U and V of the previous iteration step.
The formula in the combo overlay should in this case read: IF(EQ(ITERATION, 0), 0, A)
Combo Fraction and Combo Groundwater Depth
Combo Fraction and Combo Groundwater Depth use input from the previous iteration step, unless it is step 0. In that case, a Global value is used. The Global DEFAULT_FRACTION is used for the saturation percentage, and the global DEFAULT_TABLE is used for the groundwater level.
The formula in the combo overlay Combo Fraction should in this case read:
IF(EQ(ITERATION, 0), GLOBAL_DEFAULT_FRACTION, IF(EQ(A, NO_DATA), GLOBAL_DEFAULT_FRACTION, A))
The formula in the combo overlay Combo Groundwater Depth should in this case read:
IF(EQ(ITERATION, 0), GLOBAL_DEFAULT_TABLE, A)
Combo Surface
The combo Surface gives the last value of the waterlevel on the surface and is input for the next iteration step. If there is no previous iteration step, the value should be 0. Make sure to check the box "previous" to make sure the Combo Overlay uses the values of the previous itertationstep.
The formula in the combo overlay Combo Fraction should in this case read:
IF(EQ(ITERATION, 0), 0, A)
Combo Infiltration Speed
The purpose of the Combo Overlay Combo Infiltration Speed is to set the correct formula depending on the saturation of the soil. This example uses the overlay Ground BOFEK ID to determine the type of soil.
The formula is entirely hypothetical and only serves to make it clear that, for each iteration step, a value is chosen based on the degree of saturation.
The formula in the combo overlay reads in this case:
MAX(0, SUB(GLOBAL_DEFAULT_INFIL, SWITCH(B, 0, 1004, MUL(10, SUB(A, GLOBAL_DEFAULT_FRACTION)), 1006, MUL(5, SUB(A, GLOBAL_DEFAULT_FRACTION)))))
Rainfall Overlay
When setting the rainfall overlay, the default settings can be used. The exceptions are described below.
Rain Event Duration: Specifies the total calculation duration, which is subsequently divided into iteration steps.
Water System – Water Level: Here the initial water level and the U and V flow are set. Use the option "Advanced: Select Grid overlay to set initial water level and also flow UV".
The water level is set based on a specific overlay, which is the combo overlay Surface. Similarly, the y and x speed from the combo overlay is used as initial input.
Groundwater: Initialize the groundwater level using the Groundwater Depth combo overlay.
Unsaturated Zone: Initialize saturation and storage percentages per grid cell using the Fraction combo overlay.
Generated Output Overlays:
- Surface Last Value
- Rain
- Ground Last Value
- Ground Watertable
- Ground Last Unsaturated Storage
- Ground Last Unsaturated Fraction
- Surface Last U
- Surface Last V
- The number of timeframes is set to 1.
Iteration Collector
The Iteration Collector is a type of overlay. It shows the results of each iteration step. An iteration collector needs an input overlay, in this case it is the Rainfall overlay. One timeframe is saved for each iteration step.
The Modulus attribute of the Iteration Collector determines how many iterations are stored. By default, this is set to 1. This means that only one (the last) result of each iteration step is saved and used as a timeframe in the iteration collector. When the modulus is set to 1, every iteration is stored. When you set the modulus to 2, half of the iteration values are stored.
Indicator
The indicator sets the start and end times for the rainfall overlay iteration steps. It uses queries like SELECT_ITERATIONS_WHERE and SELECT_ATTRIBUTE_WHERE_NAME_IS_RAIN_M_AND_OVERLAY_IS_10_AND_RELATION_IS_WEATHER_AND_INDEX_IS_2 to determine the number of steps and total simulation time. The UPDATE_OVERLAY_PARTIAL_START_SEC_WHERE_OVERLAY_IS_3 and UPDATE_OVERLAY_PARTIAL_END_SEC_WHERE_OVERLAY_IS_3 queries then adjust the timing for the next step, identified via SELECT_ITERATION_WHERE. Fraction Start and End define these as fractions of the total simulation time.
Number of Iterations
Set the number of iterations in the calculation panel under the 'iteration' option. This is set to 1 by default.
Exploring the results
To view the results, play back the iteration sequence. The following results can be seen here:
- Water on ground level in meters
- Iteration Fraction: The fraction of the total water storage capacity of the unsaturated zone that is filled with water in meters
- Iteration Storage: The amount of water in the unsaturated zone in meters
- Iteration Infil Speed: The infiltration speed in meters per day
- Iteration Rain: The total amount of rainfall up to that point in the simulation in meters.
- Iteration ground table: The groundwater level in m + datum.
When the iteration Infil speed is viewed, it becomes clear that the two different soil types (BOFEK IDs) give a different result in the infiltration speed.
Notes and Limitations
Debugging cannot be downloaded per iteration but can be saved for each iteration. Specific updates (e.g., updating attributes for certain building types in iteration 5) can be executed using the API and indicator but not through TQL for non-initial iterations.
Effect of Iterations on Calculation Accuracy
When calculating a precipitation event, there may be a difference between a standard calculation and an iterative calculation, even if they use the same rainfall overlay. This is due to the way data is processed during an iterative calculation.
In a standard calculation, the precipitation event is executed in a single step. In an iterative calculation, on the other hand, the event is split into multiple time steps, for example 10. After each iteration step, the data is stored and prepared for the next step. Rounding occurs during this process, which can affect the accuracy of the results.
The water levels are stored internally in a 64-bit format, which provides high precision with 12 decimal places. However, the results are displayed in a 32-bit format, which has an accuracy of 6 decimal places. In the iterative calculation, the 32-bit result is used. This causes small rounding differences between the results. The more iteration steps there are, the more often this rounding occurs and the larger the deviation can become.
These rounding differences are minimal. If required, additional measures can be implemented to further increase precision.