A Comprehensive Survey of the Recent Studies with UAV for Precision Agriculture in Open Fields and Greenhouses
, Akif Durdu 2,3, Kadir Sabanci 1, Ewa Ropelewska 4,* and Seyfettin Sinan Gültekin 2Round 1
Reviewer 1 Report
The manuscript is well-written and clearly explains the applicability of UAV technology in outdoor agriculture. This review presents the results of current studies and how UAV technology can be and is used in field crops but these are already known to the scientific community.
The review also addresses the issue of using this technology in greenhouse crops but does not present a solution that works now so that UAV technology can be used in all greenhouse crops because at the moment there is no viable solution as with autonomous driving, research is still needed.
Sure we can use UAV in greenhouse crops that don't grow tall (flowers) and some vegetables (lettuce etc) but for vegetables that grown tall in greenhouses (tomatoes, peppers, eggplant, cucumbers) this technology would be very difficult to apply at this time.
Author Response
RESPONSES TO REVIEWER 1
Comment 1. Sure we can use UAV in greenhouse crops that don't grow tall (flowers) and some vegetables (lettuce etc) but for vegetables that grown tall in greenhouses (tomatoes, peppers, eggplant, cucumbers) this technology would be very difficult to apply at this time.
Response 1. Thanks for your remarkable opinion. As you mentioned, the type of plant grown in the greenhouse is a major factor in the operation of the UAV in the greenhouse. For this reason, it is very difficult for the UAV to perform tasks in cases where the plants are tall, or the plants cover each other and cover the other plant view, or the plants are tied with a rope. Apart from these, autonomous UAV missions for the greenhouse are quite reasonable. This explanation has also been added to the revised article as follows.
|
… Indeed, it is difficult to carry out autonomous UAV studies in an indoor environment. Moreover, the type of plant grown is also a major factor in operating the UAV in the greenhouse. It is much more difficult for the UAV to perform tasks in situations such as plants growing taller, plants overlapping each other and obscuring the view of other plants, and using greenhouse rope for plants. But apart from such situations, autonomous UAV missions for the greenhouse make quite a lot of sense. |
Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript describes a review of recent studies on the use of UAVs in the field of precision agriculture. In particular, the authors divide the field of application into two phases: outdoor UAV studies and indoor UAV studies.
The manuscript is well written and describes in a comprehensive manner the different uses and applications of UAV systems in the field of outdoor and indoor precision agriculture.
However, I recommend that the authors set up paragraphs and sub-paragraphs more efficiently in order to offer a smoother reading of the manuscript.
I suggest authors to create a paragraph, after the introduction, that describes the organisation of the whole paper. In addition, I suggest to reformulate in a clearer way also the conclusions with the paragraphs related to the evaluation of UAV applications in outdoor, indoor and Smart Greenhouses.
Overall comments
Check the formatting of the text for the whole paper.
Line 230 - I suggest you to rewrite the sentence.
Figure 2 - There are errors in the indication of the figures. Please check it. For correct formatting, I suggest you to consult the journal guidelines.
Figure 7 - Formatting captions according to the journal guidelines. Please check it.
Figure 8 - Formatting captions according to the journal's guidelines. Please check it.
Figure 9 - The figure is not comprehensible enough and also the caption of the image "Trajectory" is not readable. Please check it.
Table 3 - Verify the formatting. Please check it.
Author Response
RESPONSES TO REVIEWER 2
Comment 1. However, I recommend that the authors set up paragraphs and sub-paragraphs more efficiently in order to offer a smoother reading of the manuscript.
Response 1. Thank you for the good advice. The required revision has been completed. Please see the revised article.
Comment 2. I suggest authors to create a paragraph, after the introduction, that describes the organisation of the whole paper.
Response 2. We are grateful for your extremely reasonable suggestion. This revision is done as follow.
|
The remainder of this manuscript is organized as follows. In section 2, information is given about the different agricultural tasks performed with UAV in open fields and previous agricultural studies are discussed. Section 3 highlights the necessity and lack of UAV solutions in the greenhouse, as well as discusses previous UAV studies done in the greenhouse. Section 4 states that the SLAM problem is vital for performing autonomous missions with the UAV inside the greenhouse. Finally, section 5 discusses the entire article and concludes the study. |
Comment 3. In addition, I suggest to reformulate in a clearer way also the conclusions with the paragraphs related to the evaluation of UAV applications in outdoor, indoor and Smart Greenhouses.
Response 3. Thanks for your remarkable opinion. More clear conclusions are added as follows. Please also see the revised article.
|
Although UAV has applications such as spraying, imaging, mapping and fertilization in open fields (see Table 1), there are almost no agricultural applications with UAVs in indoor environments such as greenhouses due to localization and mapping difficulties (see Table 2). The UAVs used in previous applications were manually con-trolled and measurements were made with the sensors on them. The studies shared in Table 3 are successful studies aimed at self-localization and recognizing the environment of a UAV in indoor environments. In these studies, methodological recommendations for SLAM are presented and prediction errors in UAV poses are compared with previous studies. Indoor SLAM applications are often an important requirement in the robotics industry such as search and rescue, defense in environments without GPS access, or in the entertainment industry such as virtual reality [100,101]. However, as we know, there is no agricultural application of such advanced SLAM methods in indoor environments such as greenhouses. The need for SLAM in indoor environments arises from the need to perform autonomous tasks only with the sensors on the robot in a GPS-denied environment. At the same time, since smart greenhouses are indoor environments where autonomous tasks will be performed by the UAV, SLAM solutions can be directly applied in greenhouses.
…
Considering the lack of studies such as imaging, yield estimation, mapping, etc. in the greenhouse environment, with the UAV, which has the advantages of mobility, high-resolution imaging and cheap cost, it can be possible to collect data and make observations autonomously from the greenhouses where production is made in all seasons, using SLAM methods. This could be an exciting advance for smart greenhouses. …
Monitoring each plant or plant community with a known location by UAV and performing specific tasks for certain plants will create smart greenhouses. This requires precise positioning and knowledge of the structure of the environment.
….
As a result, a UAV that can perform autonomous missions using advanced SLAM applications may be the permanent worker of smart greenhouses in the future. |
Comment 4. Check the formatting of the text for the whole paper.
Response 4. Thanks for your remarkable comment. The format of the text has been revised. Please see the revised article.
Comment 5. Line 230 - I suggest you to rewrite the sentence.
Response 5. We are grateful for your attention and interest. The revision is carried out as follows.
|
Mapping applications for agricultural purposes are generally aimed at marking or indicating information about plants or soil in the image. Unlike this, mapping for mobile robotics, which will be discussed later, aims to determine the geometric boundaries of the environment. If the boundaries of the environment are known in mobile robotics, the mobile vehicle acts knowing its limits in the environment and also localizes itself in this environment. In order to perform autonomous tasks in an indoor environment, the map of the environment must be known. This is why mapping in robotics is very different from the term mapping in agriculture. |
Comment 6. Figure 2 - There are errors in the indication of the figures. Please check it. For correct formatting, I suggest you to consult the journal guidelines.
Response 6. Thanks for your remarkable comment. The revision is done as follows.
|
||||||||||
Comment 7. Figure 7 - Formatting captions according to the journal guidelines. Please check it.
Response 7. Thank you for your suggestions regarding our work. The revision is done as follows.
|
||||||
Comment 8. Figure 8 - Formatting captions according to the journal's guidelines. Please check it.
Response 8. Thanks a lot for your attention. The revision is done as follows.
Figure 8. UAVs designed for various agricultural tasks in the greenhouse. (a) UAV for artificial pollination. (b) UAV belonging to ADI company. (c) UAV belonging to PATS company. |
Comment 9. Figure 9 - The figure is not comprehensible enough and also the caption of the image "Trajectory" is not readable. Please check it.
Response 9. Thanks for your comment. More clear statements have been added and the resolution of Figure 9 has been increased. The revision is as follows.
|
… The trajectory curve shows that the DJI Tello drone is localized in our indoor lab (this lab can be thought of as a greenhouse) in real-time using visual and IMU data. If such applications are made in the greenhouse, the instantaneous position of the UAV is known as seen in Fig. 9. In this way, different tasks can be assigned to the UAV and the UAV can be directed to a specific coordinate. It can perform a special treatment on a particular plant at this coordinate. In this way, desired measurements and images can be taken from certain points or certain plants. The development of such applications will also make a significant contribution to smart greenhouses in the future. Figure 9. Our previous work on UAV positioning in an indoor environment [99].
|
Comment 10. Table 3 - Verify the formatting. Please check it.
Response 10. Thank you for your valuable advice. All tables have been revised according to the format. Please see the revised article.
Author Response File: Author Response.docx
Reviewer 3 Report
In this study the authors deals with UAV studies in agriculture, which have been presented in high impact factor journals in recent years, and it is seen that most of the applications for precision agriculture performed with UAVs are carried out in outdoor environments where Global Positioning System (GPS) access is available. Outdoor studies provide more reliable control of the UAV in both manual and autonomous flights. This paper also emphasizes this deficiency and provides a comprehensive review of the use of UAVs for agricultural tasks and at the end of the study highlights the importance of Simultaneous Localization and Mapping (SLAM) for a UAV solution in the greenhouse.
Significant: yes, the paper is a significant advance or contribution.
Supported: Mostly yes,
Referencing: some additions are necessary
Quality: The organization of the manuscript and presentation need some improvement.
The paper is very interesting but necessite the little modify in the text. The paper is not clear.
I suggest to the authors to exspand the sections "Remote Sensing" and "Solution Proposal for UAV Applications in Greenhouse"
Author Response
RESPONSES TO REVIEWER 3
Comment 1. Referencing: some additions are necessary
Response 1. I would like to thank you for your valuable comment. New references have been added. Please see the revised article.
Comment 2. Quality: The organization of the manuscript and presentation need some improvement.
Response 2. I would like to thank you for your valuable comment. The article has been revised in terms of organization and presentation. Please review the revised article.
Comment 3. The paper is very interesting but necessite the little modify in the text. The paper is not clear.
Response 3. Thank you for the good advice. More clear statements are added to determine the purpose and focus of the study. Some of them are as follows. In addition, some existing texts have been revised. Please also see the revised article.
|
• A UAV that works in a large agricultural area for crop monitoring, spraying, etc. should fully monitor the field, but is the UAV battery sufficient for this duty period? • Are the size of the land and the flight time of the UAV compatible? • Can the UAV operate autonomously in a closed environment and is it reliable? • Is communication loss possible during the UAV mission? • Can UAV carry loads for the mission?
…. Because performing a cooperative mission in a limited greenhouse environment with multiple UAVs will also pose a reliability problem. It is also a challenge to establish an effective communication network between UAVs …. This study, on the other hand, deals with the survey of UAV studies suggesting agricultural tasks in two steps. In the first, outdoor UAV studies, in the second, UAV applications in the greenhouse (indoor) are investigated, unlike previous studies. Attention is drawn to the necessity and importance of using the UAV in precision agriculture tasks in the greenhouse. It emphasizes that the number of studies for UAV in the greenhouse is low and offers a Simultaneous Localization and Mapping (SLAM) proposal for indoor autonomous UAV to solve this. The fact that the use of UAVs for agricultural purposes is a field that progresses very rapidly makes survey and review studies important. The important contributions of this study can be summarized as follows: • Agricultural practices carried out with UAV recently, mostly in 2020, have been extensively discussed. • UAV agricultural applications are discussed in two categories as indoor and outdoor environments. • The importance, necessity and inadequacy of greenhouse UAV missions are emphasized. • The importance of SLAM for autonomous agricultural UAV solutions in the greenhouse is explained. … |
Comment 4. I suggest to the authors to exspand the sections "Remote Sensing" and "Solution Proposal for UAV Applications in Greenhouse"
Response 4. We are grateful for your attention and interest. These sections have been expanded and additional information added as follows.
|
2.6. Remote Sensing
…
Manual methods, other than remote sensing, to obtain the phenotypic character-istics of crops directly measure data such as biomass, leaf area index (LAI), and chlo-rophyll content. However, manual methods require device operators to work inten-sively in the field and are therefore difficult and time consuming. In order to eliminate these disadvantages, technological solutions have provided significant developments in this field [34]. Remote sensing attracts more attention today due to developments in robotic technology, development of sensors, and advances in data processing. The most applied remote sensing studies are carried out using aerial images taken by satellites, UAVs and manned aircraft. With these tools, data can be collected at spatial, temporal and spectral resolutions. These tools can collect large area data and are non-destructive. Remote sensing by satellites and aircraft provides the ability to collect data on a large spatial scale, but long revisit periods, cloud congestion, and high costs limit the use of these tools in remote sensing. In addition, satellite images have low spatial resolution [47]. For this reason, recently, UAVs have become much more popu-lar than other vehicles with advantages such as flexibility of movement, ease of use, low cost, and high spatial resolution [48]. … 4. Solution Proposal for UAV Applications in Greenhouse … Although UAV has applications such as spraying, imaging, mapping and fertilization in open fields (see Table 1), there are almost no agricultural applications with UAVs in indoor environments such as greenhouses due to localization and mapping difficulties (see Table 2). The UAVs used in previous applications were manually con-trolled and measurements were made with the sensors on them. The studies shared in Table 3 are successful studies aimed at self-localization and recognizing the environment of a UAV in indoor environments. In these studies, methodological recommendations for SLAM are presented and prediction errors in UAV poses are compared with previous studies. Indoor SLAM applications are often an important requirement in the robotics industry such as search and rescue, defense in environments without GPS access, or in the entertainment industry such as virtual reality [100,101]. However, as we know, there is no agricultural application of such advanced SLAM methods in indoor environments such as greenhouses. The need for SLAM in indoor environments arises from the need to perform autonomous tasks only with the sensors on the robot in a GPS-denied environment. At the same time, since smart greenhouses are indoor environments where autonomous tasks will be performed by the UAV, SLAM solutions can be directly applied in greenhouses.
|
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The manuscript meets the requirements and can be published now that the authors have made the necessary changes.
Author Response
RESPONSES TO REVIEWER 1
Comment 1. The manuscript meets the requirements and can be published now that the authors have made the necessary changes.
Response 1. Your contribution to our article is great. Thank you for your valuable comments and support.
Author Response File: Author Response.docx
Reviewer 3 Report
The paper is clear .The authors focused on the roadmap. I recommend publication of the manuscript. That said, I would like to encourage the authors to give the paper another careful round of proofreading, to eliminate any remaining typos and grammar mistakes from the final files, starting from the abstract
Author Response
RESPONSES TO REVIEWER 3
Comment 1. That said, I would like to encourage the authors to give the paper another careful round of proofreading, to eliminate any remaining typos and grammar mistakes from the final files, starting from the abstract.
Response 1. We are grateful to you for your valuable contributions. The entire article has been reviewed and errors have been fixed. Please see the revised article.
Author Response File: Author Response.docx
