Calimate© is a scientifically proven calibration method that improves the ability to correctly perform visual estimations of vegetation cover in a pre-defined area.

Visual cover estimation is a well-established method for many areas of inventory all over the world. It’s fast, doesn’t require any tools and provides acceptable results, even though the precision usually is quite low – until now! The aim of Calimate© is to considerably improve the precision of data collected using visual estimations!

The method was developed by Åsa G Torell, while working with field inventory and daily performing hundreds of visual estimations of vegetation cover.

The basis for the web service Calimate© is a scientific article, co-authored by Dr Anders Glimskär, which describes the method and its results (Journal of Vegetation Science 20:973-983, 2009: Computer-aided calibration for visual estimation of vegetation cover).

The results show that the accuracy and precision of the estimates significantly increase after only a short period of calibration, both for individuals and between different observers in a group. The field tests also show a positive effect, especially on between-observer variation. A short while after the article was published, images suitable for calibration of tree cover in aerial photographs were also developed.

Calimate© is now a user-friendly subscription web service which can be used both by individuals and large groups. Student discounts are available.

Calimate© consists of computer generated, high-fidelity images of vegetation, where the true cover value is calculated digitally during the process of image generation.

Every image in the program is unique and is generated specifically for each user, according to the chosen settings. The user can choose e.g. vegetation types, a specific cover interval and how the results are presented.

The results from the scientific article show that the between-person variation significantly decreases after only a short time of calibration. A Calimate© session may therefore consist of as little as 20-30 images, and takes approximately 10 minutes to perform.

Our recommendation is that users calibrate themselves at least 1-2 times per week in order to maintain high precision in their estimations.

We also recommend that Calimate© is used diligently in the beginning of the inventory season, in order to assure that all personnel is operating at a consistent and high level of estimation from the start of the project. Therefore, Calimate© should preferably be introduced during the training of personnel, or at the start of a project.

When ordering subscriptions for a group of users, the group administrator can choose to automatically be notified of the results of each completed calibration session via e-mail. This enables the project leader to keep track of the calibrations and make sure that the inventory team continuously provides quality data.

If accurate data is important for your project, calibration of visual estimations is an inexpensive and time-efficient way of increasing accuracy and precision – both individually and between observers.

Visual estimations are by far the most common method of estimating vegetation cover, in the field as well as in aerial photographs. Therefore, an improvement in the precision of these estimations usually have a large impact on the entire data set.

Tests show that individuals with years of experience of visual estimations actually tend to produce larger errors in their estimations than individuals with no previous experience (Journal of Vegetation Science 20:973-983, 2009: Computer-aided calibration for visual estimation of vegetation cover), most likely due to non-noticeable drifts in estimations over time. With Calimate©, anyone – regardless of previous experience – can calibrate their estimations with the aid of a true cover value, which significantly increases both the individual accuracy and reduces the variation within the group.

Visual estimations are often critical for the morale of the inventory personnel, since there is no correct answer in the field. A calibration tool such as Calimate© boosts self-confidence as the calibration results improve.

Calimate© can be used by anyone who visually estimates cover.

At the moment, the images in Calimate© are adapted for estimations of vegetation cover in field inventory or in aerial photographs. However, new areas of application are under development.

Do you work with other types of vegetation or with something else completely, and think that Calimate© would suit your need with different image material? Please contact us! The Calimate© team strives to accommodate each user and Calimate© is constantly improving to meet new requirements!

Trademark name Calimate© registered to Deep Island Productions AB. Web service development by Haglöf Sweden AB. Scientific advisors are Dr Anders Glimskär (the Swedish university of Agricultural Sciences) and Dr Helle Skånes (Stockholm University). Web design by Stavbom De Wall Mediaproduktion AB. Background image(s) licenced by Ingram Image. Photos and screenshots © Åsa G Torell.